My mother passed away, the paid off house has a home equity loan which is more than the value of the house, now credit card companies are calling trying to collect on the debt and they keep harassing me, what should I do

So you are saying there is a credit card balance plus a HELOC which is upside down? Has her estate gone through probate? If she owed more than all her assets combined the lenders will get in line and require liquidation of assets to satisfy the loan and the credit card balance. The HELOC will likely get paid first.

You have sent then a copy of the death certificate haven't you? They can go after assets in her estate... but they can't make YOU pay for them from yours. Unless you were a cosigner.