Getting NOC when the old sponsor is not responding to calls and emails

Dear,

My previous employer applied for my HAAD license linked with his sponsoring facility. After issuing the license the employer never responded to my calls or emails. I did not get a visa or entry permit and I did not join work.

Now, I got a new job and the new employer asked for a NOC from the old employer to transfer the license. But again, the old employer is not responding to my emails or calls.

What should I do next? Can I transfer the license to another sponsor without the NOC?

If the NOC is a must even though I did not work or enter the UAE, what is the procedure?

Thanks for any help.