chkmate*instantcheckmate deduced $27.63 from checking acct., sept., oct., nov., 2012 for service not ordered. Do not know how they accessed checking acct. Called and cancelled acct. Was refunded $55.26 but denied payment Internet

Charges to my checking acct. by debit are $27.63 in sept., oct., and nov.,2012 ---november being an advance payment .  contacted co. and was refunded $55.26, but denied 1st month refund . I have no idea how they accessed my acct.  I did go to their web site to look for an address of a person who stole numerous items while doing a painting project , but did not give any personal information to chkmate.  Am changing my debit card number to avoid further charges.  Can you help in getting a refund of 1st month payment ?Thank you for being available to report these scammers !!