How company C file my H1B transfer while H1b transfer of B is pending approval, while GP of A passed 60 days.

I got laid off from Company A.
Company B filed Part-time H1B transfer, 2 days before Grace Period ends. So now I am working at B as part-time.
3 weeks later, a company C offered me a full-time job.

How should company C files my H1B transfer while H1b transfer of B is pending approval, and the grace period of A has passed 60 days?

I am in the same situation, were you able to join Company B?