He could just be nervous--- a new home is a big change for him, he's been at that shop for 3 years(correct?). Give him time to adjust to your schedule, he will come into his own and probably learn even more calls, or begin to quiet down. Most small parrots are able to learn when to be quiet and when to be loud(like when you arrive home, they can't help but be excited to see you!
)
I have also noticed that small parrots(pi's, pois, and caiques even) tend to be mimickers rather than have their own contact calls. My guys sound like cockatiels usually(due to living with one at my in laws)
and even the shop birds i have seen are like this-- our white cap pionus we have at the moment sounds like a sun conure most of the time---but then again he's competing with mollucans and macaws for heaven sakes! I'm sure he feels like he needs to be heard.