I was accepted into Penn State main campus for rehabilitation and human services but now I don’t know if this 100% what I want to do. Would I be able to change my major to undecided?
Yes, call them and ask. DUS should be easy to switch into since it is not more selective than your original major.
Ok thank you! I just wasn’t sure if I could do it this late.
Since you’ve already been accepted for summer session and are not trying to reapply for fall, and the major you want to switch to is not more selective than your original, I don’t think it should be a problem. Please come back and let us know if it turns out otherwise.
Ok thank you again! I will let you know what happens.
Hello! Also applied to penn state Harrisburg and got accepted as psych major, but then decided to change campus and they allowed me to change both campus and major again, so I think they’ll let you! Good luck! 
Yes. Because you do not actually enter your major until usually sophomore year (I think it’s like 48-59 credits or something) it is pretty easy to change major, I did it myself last semester.