If you took it to a shop and it wasn't squealing when it went in and is squealing after, take it back and have them sort that for you. They should test ride the bike to make sure everything is well adjusted and should not let a bike with squeaky brakes go out. Sometimes brakes can start squealing only in certain conditions though, so don't give them a hard time about it.
This is my number one advice generally for anyone not doing their own bicycle maintenance, if you get it back from the shop and something isn't right, tell them! They should be grateful for your feedback, mechanics are human and make mistakes, but if you never tell them, they can't learn from them.