Who's name is the contract in, and what are the ages of the persons who entered into the contract with the phone provider? If the contracting party is the husband then it's him that owes the phone provider.
A person does not have full legal capacity to enter into a contract (other than very small transactions like buying sweets or a CD etc), until they have reached the age of 18. Certainly in Scotland, the contract can only be enforced if the contract is one which is of a kind that is commonly entered into by persons of that age and circumstances, and the contract terms are reasonable. If these conditions are not met the contract is void.
You could contact your local CAB if you think either of these grounds may apply to you and/or for further guidance on how the law con contracting with young people operates in England & Wales. My guess is though that there will be little difference.
In addition any contract is 'voidable' (it may be successfully challenged) if the terms of the contract were misrepresented. If the costs of the contract were represented as being far lower than has turned out, you may have a case on the grounds of misrepresentation.
Contracts are often not as watertight as companies would have us all believe. If they were, lawyers would starve.