Battle.net and Steam asking for phone number in order to play?

[H0ll0P01nT]

I have 4 PCs setup in my basement for anyone that wants to play. I just setup the 4th and installed MW3 through Steam. I linked my account, and it told me I need a phone number to link that account through Steam. My son has one PC linked to his number. His GF has the other PC linked to her number. Well, that's all fine and dandy except for one thing. I have a spare computer, and I am not able to supply another phone for my 4th PC. Well, this limits me to only play the Campaign. Is there a work around, or do I have to pull someone off the streets for their phone number?

[ReBoot]

That's just ActiBlizz' rules. Get another phone#, play campaign-only, play a different game entirely.

[cSg|mc-Hotsauce]

Activision requires it since they came back to Steam.

You either use the one on your Steam account or your Activision account.