Tenants Keep Calling AC Company Directly

[Zana Blue]

Tenants moved in and in first month called me to complain about the air conditioner. I sent out the AC guy and he repaired it. Second month the tenants call the AC guy directly and he goes there and repairs it and they send me the bill for a service call. I call the company and say DO NOT DO ANY WORK for that tenant again unless you are going to charge them. They call the company a third time and the AC guy tells them the unit is old and should be replaced so they call me and tell me to replace it. To be fair it was old but that is a discussion that belongs between me and the AC company. So I replace the unit. Month four I get texts that the brand new unit is "broken" and that they have once again called the AC company and once more the AC company went out there. They did not even give me the chance to call the AC company myself. They told the AC company that I was a bad landlord and that I would not call them to get it fixed ! They told me they had a sick child they had to take to the doctor because it was so hot and they had pictures of the thermostat to prove it. Once more I called the AC company and told them NOT to go out there without calling me first. I am a loss as I feel I am being set up and they are trying to blame me for their child being sick because of the heat. I always acted as fast as I could to accommodate them but if they are in cahoots with the AC company I don't know what I can do ....of course they are using it as an excuse not to pay rent. How can I make the AC company stop running out there every time they call?