Sim only Vodaphone contract purchased with Phone house SPAIN. Includes roaming europe

Was informed when purchasing this contract that I could make calls from Spain to U.K. Mobiles also SMS and have no extra charges.
Received a very large bill and after making contact with Vodaphone was told I had to pay for international calls.
Was again informed by staff in Phone house that I should not pay for calls to U.K. Mobiles and that the contract allows calls within Europe.
What should I do now ?

Argue with Vodafone. Not much you can do really.

1) Argue with them about paying it.
2) Pay it.

Vodafone doesn't care what Phone House told you. You used the services, you're required to pay for them, your only real hope is they meet you somewhere in the middle and reduce the charges.