Xiao bai tu, or anyone knows? please help me!

ATT phone company sent me a double bill which due to June,2007. In fact, i

already paid my previous bill through my debit card by calling the

representive on May. ( i had a confirmation number, and my bank statement

also proved that i had paid the bill.)first, they ask me to fax those

provement to them, then i can get the correct bill. I did that at once,

then they said the number and bank statement which i sent to them is not enough.

they asked me my debit card number to check something.If i don't follow

their direction, they will disconnect my phone.why should i give them my debit card number? what should I do? Do they have right to do that? plese help me,i am waiting, Thanks a lot!