Service call client mad

So to start off I had to drive a hour and when I show up the problem was that the pump was making too much noise, come to find out that it’s clogged and having a hard time pushing everything out so I clean it and then I quote up a new pump just incase they wanted a new one as this one is really old so I tell her I’m going to do my paper work outside in the parking lot then like 40 minutes later she tells me you better not be charging me for being in the parking lot for 40 minutes. “ did I do something wrong here cause I’m still new to this trade “