Help and advice needed

Hi wondering if anyone can help.. I had my car booked in for a service all It needed was oil and filter I have got proof it got done 7k miles ago but though as it's my week of work might aswell get it sorted along with a mot.. Now had a horrible experience with the garage for a start but when I've checked my recipt he's charged me and presumed he's done a engine flush :worried: all I've read is bad things is was whytes if that helps ? It's only done 66k .. I've done 30 miles ish in it so far and no troubles ?