Best Tankless Water Heater Options in Dallas TX

I contacted NTX plumbing to ask them to fix my tankless water heater. They informed me the that they would charge $200.00 for the inicial assessment to detect the problem. They missed the first appointment, called me at the end of the day asking if I wanted to reschedule and I agreed.They were on time this time and the gentlensn who helped me was very friendly and polite. Said he would send me an estimate within a couple of days and collected the $200.00 . It's been seven days and I haven't received any communications from NTX plumbing. Now I have to wait for another company to come assess the problem and PAY for that assessment AGAIN.I couldn't be more dissatisfied.