Converting from 1000 Min Value Talk & Unlimited Data (Family) To 100 Min 5 GB Plan

Hi Everyone,

I'm currently on the 1000 Min Value Talk Family plan with unlimited data for 2 phones.  The person who I share the plan with are looking to separate each of our accounts to a individual plan, but notice the unlimited plan is for individual is higher then the family plan I'm on, based on total cost per line

Since this is more then I want to pay, I was looking at switching to the 100 minute 5 GB data plan & had a couple of questions.

1)  If I switched to this, can I keep my same number, or would I need to order a new Sim, get a new number & cancel my existing account

2) If I switched to this, would this be billed by Tmobile, or would i need to buy a $30 prepaid card (minimum) every month?

Thanks