这几天正想着退出TMOBILE呢，因为这里的信号实在让人难以忍受。。。跑题了

原来的sim应该不能再用的，上面应该是有你手机号码的，once tmobile enabled one sim, the other one got disabled for sure.

I dont think you can drop off the plan.  They may say you can get another phone, but you will have to stay with the plan (unless you want to pay for early contract termination).  Give them a call.  Their CRs are pretty good.