Presumably, an un-registered, non-contract, pay-as-you-go number is safe, unless given as a contact to other companies, in which case, how dare they sell it on! I've avoided "registering" my number with Vodaphone for that very reason. I contacted them once via the net, 'koz I was getting some mystery texts that were complete gibberish and they said they couldn't help me unless I was "registered" with them. No thanks. Problem stopped, anyway.