How do I inform future job prospects of my situation without implicating my former employer?

I resigned from a job for personal reasons, gave two weeks notice, was asked to give an additional week and I did. I have had over seven interviews, five of them stated that they will get back to me after checking my employment verification.

Two prospects called me to inform me that my recent employer stated that they were not aware of me being an employee and the second prospect informed me my previous employer stated that I should not be hired for anything but a low level job.

I have never had a write-up nor complaint of my job performance; my attendance was excellent,I was always on time and completed my tasks. I was even promoted to open and manage a new office.

I have two interviews scheduled this week and I need to know what to say to cushion my former employers retaliation against me. Please, please help me? I wish I had the money for a quick response however I am unemployed and struggling to survive.

I am about to lose everything I have if I don't get a job within two weeks. Please.

Thank you.