It is understandable the fact that your new employer wants to get some references about you. There were cases in Hamad Hospital (a while ago) with staff who was bringing fake certificates/diplomas and they actually didn't have anything in common with the job they were hired for.
But you can ask your new manager to not call your old company until you will not submit your resignation, I am sure he will understand, we had similar cases also in our company.

Goog luck!