Here's an alternative explanation:

Maybe he deliberately switched it off as part of his routine maintenance/inspection and forgot to turn it back on at the end.

When you called him, he suspected he had done something wrong, but wasn't sure what it was. Whatever it was, he was embarrassed about it, and he hoped to avoid making the situation worse, and making you angrier, by making you do all the work of diagnosing the problem and fixing it. That's why he wanted to do it himself.

In any case, he wouldn't have charged you for the second service call.

The part about "inadvertently hit the switch while he was putting his tools away" was a lame excuse, but it was motivated by embarrassment, trying to explain away a stupid mistake, not by wanting to cheat anyone.

Too bad your mother called you instead of calling the company directly. She got you riled up for nothing.