There's likely a back door installed somewhere so deleting random files and changing passwords will not help. You must eliminate the backdoor code. This can be very difficult to find, they can be very cleverly hidden.
Start working through the steps in FAQ My site was hacked.
If you have further hacked site issues it's best to post in the Troubleshooting forum. This hacks forum is not for your kind of hack. I know it's confusing, don't worry, it's no big deal.