Can a doctor refuse or decline to do BBL revision? How do I go about talking to him about this? (photo)

The best approach is to ask in a respectful way for revision at a reduced cost.  The surgeon may not feel that anything more can be done.

Ideal candidates are at a stable weight,  in good health , and have excess fat in some parts of the body and too little in other regions.  Gaining weight before the procedure is to no advantage and when you lose weight again the fat cells will shrink just like the donor site fat cells.  Typically, the transferred fat results in a significant increase in volume of the body site being treated.

Hello JeanRK31 - Typically before a surgeon will do a revision, it is important to wait until all swelling has subsided, this usually takes 6+ months. If your surgeon feels he cannot offer more, then you can always seek a second opinion from a board certified plastic surgeon. Your surgeon may have seemed hesitant being that you are early in your recovery period. Please be patient throughout this time to allow for swelling to subside. Best wishes.

First I would wait 4-6 months total from your original surgery. If your surgeon feels he can not offer you more, then perhaps you need to see another surgeon.