I'd ask the supervisor/tech support guy why they think it is your fault (they may have additional technical information that you don't know about). It's interesting that you state that your PC has been hacked. Are you sure that is the case? For example it is possible you have a trojan on your PC which has sent details of your account/password to another party, and if so changing your password isn't going to stop it happening again!
There is a big difference between your PC being hacked as opposed to there being a problem with the security of your ISP.