Can a creditor garnish my wages if I am already on a settlement payment plan with them and making the payments regularly?

It can be possible for a creditor to garnish your wage but highly unlikely once a settlement agreement is made due to the breach of contract claim you would have against the creditor.

I do not understand all of the facts involved in your case, however generally a creditor will not garnish your wages or take undertake any other collection activity if you are satisfactorily keeping a settlement payment plan with them. The problem is that by the time a settlement agreement is reached, and commonly reduced to a judgment, the creditor has very little patience left. Therefore, if there is any default in the payment program they will consider it reached and take all available actions immediately collect the remaining balance due. If that is the case here, perhaps engaging in attorney, including my office is, might allow the potential of resurrecting the settlement agreement. As I do not have all the facts, and having seen none of the paperwork, it is impossible to give you a firm opinion.

The answer is dependant on whether you entered into a judgment with the creditor and what the judgment says.