Anyone know any service who offer sms registration like ppl send sms , get activition code to complete registration on website?
Any SMS gateway would do it. If you would like to do payment processing upon activation, then you need special contracts with the companies.
Why dont you buy your sms gateway there are many sms gateway provider which will give you api for that
Check out this link http://www.developershome.com/sms/smsGatewayProvComp.asp hope its will help you..