help with vodafone bill?

[xxsxxm]

ok so i live in the u.k have a contract with voda for 25permonth unlimited texts and 500minutes, also 50p per day to use the internet, i went abroad to spain amonth ago and used the internet quite abit facebook and stuff, today my fone has been disconnected and after ringing voda there sayin i have a bill of 552quid!!!! aparently for intenet use in spain as spain charges are alot higher, thats nearly the same price as my frickin holiday! i cannot get my fone on until i pay? what happens if i cancel they direct debits with them will i just get blacklisted from them, i do not have that sort of money any help please