Could I use $30 walmart plan?

Hi, I am okkeum.

I want to know about $30 walmart plan.

Now I use $50 plan but in my home there is no signal, so unlimited call is useless for me.

So I want to use $30 walmart plan which gives unlimited internet and 100mins call

Is it possible to use walmart plan with my number?

To get $30 plan, should I get new SIM card?

If so, after changing SIM card, will my phone number change?

I wait reply.

Okkeum Lee