Contract cancelation

I have been calling to since November to cancel my contract that was ending in January,because they say it must 30 days advance,now they deducted 547 in February of which they said January was my last payment date,I only canceled one contract of which they were two and left with 1,which I must pay 320,not ghey added other amounts of which they are lying says its tax and the statement say different, now they say I'm in arrears and it affects my credit score because of their mistakes, please help.