First, they probably don't have your work phone. Second, if they call work, you inform the boss what is going on. Provide the paperwork that has been supplied to you - the boss most likely knows that you weren't in Micronesia during that time, because you were WORKING for him. Third - get the boss to threaten legal action against the "creditors" for interfering with his place of business. It's almost certain the mere threat will scare them away - if not, get a lawyer to summon their asses to court in your home state. When they fail to show, the judge finds against them, and suddenly they owe YOU AND YOUR BOSS!!
This sounds like easier money than patent trolling. Think I'll switch my SSN to 000-oh-baby