Hi buying from uk iphone 3gs but i need to be register?

My friend said i need to be register if not they charging to much

Hi if you are buying a phone you always need to register your phone a carier or celluar service so you can talk, text, and, online internet. Take your phone to T mobile and say "i want to register this i phone to your network. If you already have a celluar service or carrier please please let me know by commenting on thiss awnser!

Sorry i'm in Singapore i need to be use for Singapore network but my iphone 3gs i buying from uk but when i inset my Singapore network sim they charge any with out using but my friend said i have to register but i don, t know how can do for register please give any clue