When transferring pre-paid number to contract account, do I need to cancel pre-paid?

Hello,

I have been on prepaid for a year with o2, and now I have got a contract with o2 as well. I have asked to keep the old number, which will be transferred next week. Do I need to do anything to stop my old account, or will this be automatic once the number is transferred? Also, I have just over 20 Euro on my prepaid account, do I need to do anything to have that transferred, or will it be automatic as well? Thanks.