mobile phone contracts

[brian.f]

Does anyone know the usual period of contract for a mobile phone, and can it be legally challenged when no signature to the contract is obtained by the phone company?. My wife terminated
with Singlepoint last March, whereupon they added £1,300 in what they call 'unexpired line rental', but they can't show me a contract that say's she has to pay that amount for a service they aren't providing

[BexTech]

Contract is usually 12 months, as for signature depends on whether the contract was 'signed' in a shop, or if done over the internet, by phone etc.

Singlepoint has now been taken over by Vodafone.