I don't know why are you considering studying in a post secondary program waste of time and money.
because you have already completed graduation and after graduation its better to apply for either post graduate diploma or masters program.
anyways can you tell me if I change my program from post diploma level to post secondary level, will that create any problem for me??
I think it can creates problem because post secondary program is lower than the bachelors degree. You have to explain in your SOP with strong reasons that why are you interested in post secondary program after graduation.