Mr. Appliance of Park Slope

We had been in contact with the manufacturer who gave us this company to use. They came and cleaned the drain basket and took some excess water out from a tray under the dishwater that had accumulated. He stated there was a gasket missing from the non return valve, but stated that he would need to contact manufacturer to order part. I asked if he had the part and he said no. He instructed us to clean out the drain waste to help with the issue. He left saying that the machine should work fine now. After we used it the first time, it was still making weird noises and not working correctly. He said that if we still have problems to give him a call back, but I certainly will not.

I called Mr. Appliance to fix my fridge that was not working in December.   They came promptly and seemed to diagnose the problem and replaced the sensor they deemed faulty.  Two weeks later the problem was back and they came back and tried replacing the sensors again.    
Now two months later the fridge is not working again and they want to charge me another $110 service charge to come out when I have already paid $400 for the prior "repair".  Clearly they do not stand by their work.  They claim to guarantee their work for 90 days but their most recent visit was within 90 days (and the first visit just over 90 days). I don't believe they diagnosed the problem correctly and now I am stuck having paid a lot of money and still not having a functioning fridge.
UPDATE:  After I called another repair company they diagnosed the problem as the heater - not the sensors - leading me to believe the sensors were not a problem in the first place.  Furthermore the repairman showed me how the sensors were replaced incorrectly and very sloppily by Mr. Appliance.   Mr. Appliance has refused to refund my money or come replace the sensors the proper way.