How do i change my phone in account from monthly to annually and keep my phone number?

I subscribed to a phone-in account using the $2.99 monthly billing, but now I want to change it to the annual billing instead. How can I do this without losing my current phone number?How do i change my phone in account from monthly to annually and keep my phone number?
SLW, there are so many companies with so many different plans.

You would be best to ring them directly and ask what options you have to do this.



I'm sure you cannot be the first person to ever want to do this - so state your case!