How do you keep your old phone number with a new cellphone?

I changed my service from Virgin Mobile to T-Mobile, and I want to keep the same phone number I have. How do you do this? I called Virgin Mobile for my account number, but they are claiming my account number is the same as my Vkey, but I doubt this is right. How do you get to transfer your old phone number to a new phone? Thanks in advance.

sim card, but i never changed my sim card with a different company, but with the same company

you can not kepp ur old phone number on a new phone. For example:

If you have a plan or pay and talk with telus and you switch to bell u cant have the same number.

I don't think it is possible with different phone companies

I'd say that's impossible. It would only work if you stayed with Virgin Mobile and get a new phone.