I am not getting my rental advance back

Hi

I stayed in a Apt for about 2 yrs at that time we never had any pest issues ie cockroaches or bed bugs)so now we vacated Apt on 2nd Aug , on that day inspection was done and we were informed that everything was good and we will receive our check soon.

But now they leasing office people are telling that they cannot give our money back as they found some cockroaches on 23rd of Aug. and they have done some pest management twice.They may even leave a bad remark so that we may not stay anywhere else.( they say that we tenents have not informed them about those pests)

Please help ! are we responsible for pests if they come after vacating the Apt.

Thanks !