Paypal offers an identity verification feature where a cell phone is checked against a given billing address.
I would like to have a similar verification system in my website. What do I need to do to get this type of validation in place?
Cell phones numbers aren't intrinsically linked to mailing addresses; the association is stored by the company that does the billing.
So if you want to verify the phone against the cell provider's billing address, then you would have to get that information from the cell provider. If you want to verify it against the billing address of the credit card the phone company uses, then you'd have to ask the credit card company (once you have the card number from the phone company).
As a rule, companies don't make address information available for you to query. The exception is credit card companies, which will do address verification as an anti-fraud measure. This verification happens through your merchant account through which you process card transactions, and may be subject to certain conditions worth paying attention to.