Slaves are not allowed to "work off" debt. There was no escape. Your family history sounds a bit dubious at best.
Not my family my wife's ancestors. They didn't "work off" debt and I never implied that they did.
Again their travel was entirely paid for, they were not "in debt" to anyone. They were headed to Philly but Andrew Tarbett a shady ship captain conspired with Alexander Spotswood to pocket the money and sale them into slavery in Virginia.
When the criminal endeavor was found out the people that were left alive were set free.