Switching majors after transferring?

Realistically, how easy is switching from an impacted to a non-impacted major in L&S? I’d like to attend UCLA but I was accepted for psychology and have decided I want to major in mathematics instead. UCSB has already switched me from psychology to mathematics. I don’t know if I’ll be able to do the same at UCLA and don’t want to waste a year of my time.

I already know the formal answer to this question, so a link to the math department’s phone number is not what I’m looking for. I want students’ opinions. I should probably mention that I am currently completing Calculus II. I will have to spend the first year at UCLA finishing up lower division math, i.e. multi-variable calculus and differential equations.

I know it’s unlikely I will finish the math major in time for graduation. I’m okay with spending an extra quarter or two there if the math department is. It would be a shame to turn down UCLA if, in reality, switching majors is no big deal. I just want to know where I stand before I make any important decisions. Thanks for your help.