Your best solution here @haris7 would be to complete a change of ownership for the number you are using by following this link Change of Ownership providing the credit check goes through, the number will be in your name the following day. Please be aware, it will only be for the number, if you have a device, this will be a credit agreement.
If you prefer a new number visit a store or take out an Evo contract with a phone online here Evo but this will mean cancelling the contract you are already paying for.
Worth taking a look at Voxi, still Vodafone here: Voxi
As far as checking if you would be credit check cleared, take a look at your credit file, I can look at mine through the banking application, although companies don't generally go by the score, it gives some indication. Vodafone will look for some UK credit history, a UK address and being on the electoral roll at the address helps. Further information from Vodafone here: Credit Checks
