Blackberry BBM question

[SecretSquirrels]

Totally ignorant about such things .
DS2 wants a new mobile for Christmas, his old one is broken , he uses it very rarely and is on Tesco PAYG at the moment.
He says he would like a Blackberry because you can send free messages. How does that work? Does it work with PAYG? Surely it must require internet connection and isn't that expensive on a mobile?
We have very poor signal at home but do have wi fi.
I can get a good deal using Tesco vouchers at the moment.

some service providers charge nominal fee each month on payg t mobile do a sim top up 10 pounds get free bbm for 6 months do not need internet do not have wifi on mine turn it off get from tescos go to independant phone shop to get unlocked then shop arounf for payg chip

Thanks

Blackberry provides a service called Blackberry Messenger (BBM) where Blackberry users can message eachother written, picture and audio messages for free (dependant on an add on being purchased for PAYG or included in the tariff for pay monthly) Virgin charge £5 for a monthly subscription, the T-Mobile the previous poster mentioned sounds too good to be true so maybe dependent on additional top ups (i.e if you top up each month or something)

Sorry just to add, you might be better off buying the BB from tesco and swapping for a sim card from another network, cheap enough to have the phone unlocked on the high street

Thanks Happydog.
DS never used his phone much before. I think the £10 credit he put on over a year ago is mostly still there. If we have to pay £x per month for BBM then it's not exactly free.
I wouldn't have bothered to change his phone but the old one is broken and I prefer him to have one when he's out.