Recently I got accepted to Umass as undeclared with natural sciences track(second choice major). Is it possible that I can switch into computer engineering after a year.
Check their transfer policy. College department transfers really vary, usually transferring from a competitive program to a less competitive one is more possible than vice-versa. Not saying the latter is impossible.
The process will require you to have good academic standing after a year, and you may have to write a ‘Why transfer’ essay.