Security cheques misused by the opposite party What to do

i had issued 5 security cheques at the begining of a transaction with a company mentioning in the covering letter that they are for safe keeping and not to be presented. they supplied inferior material and in much excess of the quantity that i asked for, i gave them the payment by e transfer for the agreed sum with the consultation of the in charge of that time. the company sacked the in charge and deposited my blank cheques by filling the amount the proof with me is the cheque book in which the details of the cheques are written as blank cheques gives to party and email send to the company