There are two issues here:
(1) The fee. Did you agree to pay your attorney hourly? If so, have they billed you for that many hours? IF you hired them on a flat fee basis (which is rare in contested divorces), there may be an issue. Your engagement letter with the attorney should spell this all out.
(2) Withdrawal. An attorney can withdraw for many reasons (including not being paid, not getting along, etc.). What did the lawyer say? You can oppose the withdrawal, but it will likely be granted.
Talk to the lawyer. See if you can work out a resolution to the fee issue and then go find an attorney that wants to help you.
The analysis would start with the engagement agreement (if one exists). The analysis would continue with the amount charged for the tasks undertaken. An attorney is only entitled to receive a reasonable fee. If the fee charged is more than would be reasonable, then the attorney is not entitled to the excessive amount of the charge. The analysis would continue as to the understanding that you had with the attorney. If the attorney was supposed to undertake certain tasks for the money that you paid and the attorney did not do so, or the work was incomplete, then you may be entitled to a refund.
An attorney is not an indentured servant. That means that the attorney can generally withdraw from representation if the attorney and the client develop a conflict or the attorney has some other reason for withdrawing from representation.
However, the attorney does owe the client a duty to be responsive (return telephone calls, respond to emails, etc.). A lot of attorneys get in trouble for not keeping a client informed.
You should write a letter by certified mail, return receipt requested to the attorney to set out the facts, and to request the relief that you want. If the attorney is non-responsive, you can use the letter as evidence for a grievance.
If you have a grievance, you can follow the procedures set out at the Texas State Bar web site at the following address: