I have a lender trying to collect money on an account that has a wage garnishment. Do I still have to pay them a monthly payment if they are garnishing my wages?

Normally the garnishment was because you not paying enough ? So should you be paying, yes, but there is nothing legally more they will do, beyond garnishment

No, you don't need to making additional payments beyond the garnishment. But the sooner you pay the judgment balance the sooner the garnishment will be lifted.

If you are making monthly payments, that suggests that you have reached such an agreement with them, and such agreements normally are for making the monthly payments in lieu of garnishment or execution.

So you should contact the attorney for the judgment creditor and insist on knowing why they are garnishing your wages.