witness

I need to ask that in the family case the plaintiff (lady) while filing a case, give a list of ppl, who will appear for her support witness/ gawahi in her support, while she file the case. At the time of submitting the affidavit they changed the person themself, and add another person who submitted affidavit, and removed the persons which where mentioned while filing the case. Is this allow as per law. My lawyer refused to do (Jirah) on that particular person, mentioning that ther person was not initially in the list of witnesses. The other party had submitted an application now. Please tell if its allow as per law to add a person at later stage as a witness. Regards