If a creditor claims they sent 14 bills before sending your debt to collections but you only received two bills can you dispute this?

If the account was in default due to failure to pay it is unlikely non-receipt is grounds for argument. Were the two bills received paid according to the agreement? Even so, the debtor knew the account/debt existed and money owed. The person could try using the lack of communication as a defense but it would be a flimsy one at best.