If you found that your lawyer has colluded with the opposite party, then nothing prevents you from changing the lawyer.
For that you issue a notice to him stating that you are terminating the vakalatnama given to him and demand him to give NOC and not to apear in the case anymore on your behalf.
If he is refusing to give NOC, you may file a memo before the cout directly as party in person and inform court that you have terminated the vakalatnama given to that lawyer and permit you to appoint a new lawyer and request the case to be adjourned for this purpose.
The court will accede to your request.