never served, if vacated, can they re-serve

Okay, so I received a phone call the day before Mother's day May 12?) saying that I owe $1200 and to pay up now...Don't know who these people are, and never heard a word of this before...They said that my ex told them to call me and collect. Apparently, he took out a payday loan in 2002. On a check that was a :x secret bank account - more on that later - They notified him at least 7 times that I can tell, probably a lot more. I tell them not to call me anymore and change my number...they send letter demanding payment - I send letter telling them that, per divorce agreement, he is responsible for debt, as he hid assets and debts throughout marriage, they send letter demanding payment, I send letter asking for validation, (ha - am begining to research out my rights now) no response. They then send out letter to my first request of don't call me anymore - telling me that they already have a judgment against me and will hit my credit with bad juju on June 4th....I go down to the county courthouse, and sure enough, they filed back in 2003, served the notice to his mother at her house, because the check he wrote the payday loan for had her address and phone number with his name, (not my name or info. anywhere on the account) so all correspondance went to her house. I didn't even know that this bank account existed until last Friday. Soooo, long story longer, the statute of limitations is not up until 11/08, if I go to court to get the judgment vacated, will they just serve me again? I never knew anything about this, they served his mother, not me, at an address that I did live at for about 3 days before the divorce, (he moved us in there, another longer, more boring story) left 4 months prior to her being served AND filed divorce docs 2 days before this suit was first filed.