Help needed with dentist's/implantologist's treatment.

Quick backstory: my mum got braces a few months after I did because we thought the orthodontist seemed good.

She also needed dental implants and this orthodontist had an implantologist that he worked with, so we got implants done by him at our orthodontist's office. She needed 5 implants (3 upper jaw, 2 lower jaw). We were told by the orthodontist that all would be Osstem implants, but later when I asked for the bill after the implantologist performed the surgery, I saw that 4 were Osstem, and one (a front implant) was from a brand called Implant Genesis. My orthodontist had earlier assured us that they would use Osstem implants. At no point before, during or after the surgery did the implantologist tell me or mum that they were putting in a different company's implant because of size issues. I only got him to admit that when I asked for the bill with the implant serial numbers. The office also charged us the same price for all implants. This is in Mumbai.

Is it normal for a doctor to change the implant brand without informing the patient? Do you think this situation justifies a legal case? If so, how do I proceed?