Why would they not replace the contactors? They'll go out again and you'll pay another service call. If the air handler is only 5 years old, there is a good chance that it will match up to a new heat pump. I would not call back that company, not replacing the contactors is dumb. I would find somebody of a reasonable amount of intelligence to see if the fan coil can be matched up, it may not be possible, but I sure wouldn't rely on the other company to be able to investigate.