sky

hi i had sky for lots months. i dont have a direct debit set up as my account does not allow them. i was late paying my sky by a few days. i paid it 3 days late. they turned my sky off. i called them up to ask them why and they said they refuse to turn me on till i have paid 2 months in adavnce. i have paid for this months service and i am not recieving it. they have been happy with me to pay every month by card. they have never said this before. what can i do. they want me to pay 2 months in advance or theywill make me pay the rest of the year as its a renewed contract. i have had sky about 2 years. i have also paid for this months viewing without recieving what i have paid for