Can I interchange the sim cards of my new two cell phones using the same provider and how?

I upgraded my old cell phones to an LG and a Sony Ericsson with separate lines and made a mistake in assigning the existing numbers of my old phones to each new phone during activation. I tried switching the sims cards but didn't work. The Sony was activated using my regular number but I prefer to have the LG.

Can I interchange the sim cards of my new two cell phones using the same provider and how?
Take it to your local cell phone service provider store. Using their computers, they can reset, reactivate, and switch the SIM cards. Just explain to them exactly what you want :)