Failure of Attorney

I would like to present a question to our community.

What would/can a client do when an Attorney fails to return calls, e-mails and all other types of correspondence?

My bill is very small and I have even tried to speak with him re: full payment and he still will not return calls, etc.

His lack of communication is causing me (a divorced father of two boys with temporary sole custody) to lose, what I feel is, precious legal ground.

Any help, comments would be greatly appreciated! I am also available for comments off line

Thank you very much for your time.