Florida is a "deficiency judgement" state so unless the lender specifically forgives you "in writing" they can absolutely go after you for any deficiency. I would think the PMI company could do the same but the interesting thing is they should have been involved in the approval process so it's odd to hear that they are contacting you "after" the closing.
I would not give out any information over the phone. This may be just a sleazy collection agency that the PMI sold of the collection to.
Here is an attorney that specializes in asset protection and bankruptcy. Depending on whether they go after you, you may have to file bankruptcy:
All the best,