10% of calls nonsense
They cant only do it for people who make more than 10% of their calls to the numbers as in the contract there is a clause stating that if they charge more for inclusive minutes you can end your contract with no penalty.
So don't take that rubbish look up the contract its clause 8.4 (c)
(c) you are a Consumer Customer and we increase charges for calls, messages or
data that form part of your inclusive allowance or your Line Rental Charges or
change this Agreement to your significant disadvantage in accordance with
paragraph 9.2 of the General Terms, provided you give us a minimum of 30 days’
written notice (and provided you notify us within one month of our telling you
about the changes). This does not apply where the increase or change relates solely
to Additional Services in which case you may cancel, or stop using, that Additional
Service.
http://www.o2.co.uk/assets/O2HybridNav/Static-files/PDFs/newcontract.pdf