Dropped off my aircraft to get my audio panel issue checked out at Sarasota Avionics. There were several items that had to be addressed and Matt (the Sarasota Branch Manager) assured me to get everything figured out. After the first week passed by and their work pace was already beyond ridiculous and they haven't even started on the actual issue yet, I thought I will give them another week to figure out the issues to ultimately come up with a plan. They had two mechanics working on it and both told me that they are required to remove all my current audio jacks (which are typical for a helicopter) and upgrade to LEMO Bose jacks. Both knew, that my company is OAS carded and each aircraft needs to meet certain minimum standards to stay carded (including audio requirements, so State employees have the option to use their helmets during flights). I asked Matt if he is certain about this upgrade and he assured me on several occasions that I am able to use adapters in the future to keep the helmets operative. After several weeks of work and (which was supposed to take less than five days), I finally received the aircraft back again and we returned it back to service. However, on the first flight already, I had a weird noise in the tail boom and the audio panel was working intermitted and only compatible with BOSE Headsets and NOT a helmet or headset with helicopter jack as they said before. I had to return back to the airport and lost the first contract until we had figured out what the issue was. I couldn't believe my eyes when I saw, that the mechanics of Sarasota Avionics left their tools in the tail boom and "apparently" forgot about it. To make matters worse, I have finally seen their *** work and they had drilled holes in the cross-bars inside the tail boom to mount the GDL44 (which btw. is not the correct position per STC!). Once our Mechanic took a look of their work and using proper Maintenance Manuals on his side, we figured out that it is illegal and against all "Standard practices" to drill holes in a tail boom of a helicopter. To give you a ball park figure of how much a tail boom is worth, we're talking about a price of over $100k! We called the FAA and they had sent out one of their FAA investigators down to inspect the work. After the visit of them while having the manufacturer on the phone, we were required to repair the damage based on an engineering drawing, provided to us by the Manufacturer. The costs were in excess of $5,000. Within the same week I received an invoice from Sarasota Avionics of more than $8,000 for their work. I immediately confronted Matt about these issues and findings and he promised us to take care of it right away. ...however, weeks passed by with no update whatsoever. Then, there came another invoice with a reminder of the outstanding bill. This time I took a witness with me and had another conversation with Matt and he assured me to take care of it right away and that I should ignore the invoice and he was very busy the past months. During the wait time we had several jobs to fly, however, with very *** audio and several issues during flights. We were required to purchase 7 new Bose A20 Headsets (approx. $7,000 in value) in order to be able to communicate with passengers during flights. We have had recently a very important state mission to fly which required us to wear helmets during the operations. We had to improvise and use handheld radios with special cords to communicate with each other. It was so embarrassing, that we actually had to cancel the contract due to communication issues and the contracting party cancelled the flight. The state department requested us to get this issue fix immediately prior to any further flights and we were required to contact another Avionics facility in Tampa (Tampa Avionics, Inc.) to fix the issues we had so far. Sarasota Avionics was still not able to come up with a solution and we were stuck with extensive costs we had to pay for a brand new audio panel (GMA 340H) (that was actually approved for this aircraft), as well as "down-grading" to the old helicopter jacks to meet OAS requirements again. Tampa Avionics provided us proof that the Audio panel that was previously installed by Sarasota Avionics is approved for fixed-wing aircraft only and not certified for helicopter. Again, we lost about $3,500 and spent $7,962.40 on repairs to fix their messed-up work. Ironically, a day after Tampa Avionics successfully finished their work in record time, a new employee and now Branch Manager "Larry" (Matt got fired in the meantime!) showed up with an invoice in his hand, asking me to pay the outstanding bill immediately. I explained him the situation and the fact that I'm not going to pay them for this mess. Finally, the owner "Kirk" called and was requesting a meeting with me to discuss the issued that were ongoing for over 8 months now. From the first minute on, he was just rude and unfriendly to me, our pilots and staff. We had setup an appointment on a Monday morning at 9am to meet each other at our office facility. However, I was stuck in traffic and emailed him ahead of time that I will run a bit late. He immediately got aggressive and threatened “to find me” if I don't show up right now and that he has other stuff to do instead of dealing with me. I ignored this message and took my time to the office. When I showed up, I explained him that I would like to keep this conversation professional. I was expecting at least an apology for the past months and the issues we had and thought they may come up with a mutual agreeable solution to get this issue resolved. However, once he started talking for awhile, he clearly got more and more in rage and called me and my wife an "***" and "***", then stepped up in my face and started attacking me. I removed him from my office and his partner called the police. The good thing was, that our premises are video and audio recorded and the entire situation was captured. I advise anyone that needs Avionics work done on his or her aircraft - take the time and make the necessary research! Never pay upfront! And most importantly, don’t believe what they say. Call Garmin to double check their stories! ITS A WARNING TO ANYONE HOW SHADY AND UNPROFESSIONAL THIS COMPANY IS. I have contacted several other clients that got ripped off by Sarasota Avionics in the past and we all agreed to get the FAA involved. I know first hand, that their FAA 145 Certificate is based on the operations in the first floor of their building. The second floor, however, is used to store parts, that don't have legal documentation and the FAA never knew about those illegal practices. It's time that someone steps up and stops that business!