Will my current phone automatically switch to the prepaid plan if I put in the SIM card?

I'm currently on a monthly plan with my T-Mobile phone and want to switch to a prepaid plan. I'm planning on buying a SIM card for the prepaid plan. Is that all I have to do to switch to a prepaid plan? Are there are any other steps I have to take and any extra fees?

The phone handset itself should work fine as a prepaid phone by putting in a prepaid SIM card. However, keep in mind that activating a new prepaid SIM gives you a new number and doesn't cancel your current monthly plan.

You can call T-Mobile and actually have your number converted to prepaid without buying a new SIM. This cancels your monthly plan, and if you're under contract there's a termination fee ($200.)

If your phone was bought from a store it can work with any sim card however if you bought your phone from a wireless company then it can only work with the sims from that particular company but don't worry if it doesn't work there are places where you can go and have your phone deblocked so it can work with any sim cards and you can also do it yourself it you research it well on google.

I have at&t, so it might be different, but when my phone broke i bought a go-phone (prepaid) and slid the sim card in from my phone that had a plan on. The prepaid phone automatically picked up signal and i never had to do anything to it or pay any fees.