Ay, ganyan talaga nangyari sa akin with my second! 3 months pa lang siya pero after a few weeks of EBF, biglang ayaw ng bottle kahit Enfamil pa, siguro na-spoil siya sa breast kaya ayaw ng latex/silicone. I'd try switching bottles first (maybe MAM or Philips Avent nipple shapes are different) bago pa lang palitan ang formula, kasi sometimes it's really the bottle nipple flow na problema, not the milk itself. A few of my mum friends swear by trying the bottle with warm milk pa lang, or kahit simpleng patience, try offering it when LO is not too fussy, and mag-insist lang for a few days kasi eventually they adjust. If gusto mo ma-sure kung milk intolerance or dairy issue talaga, best na mag-consult ka sa pedia before switching formulas, para sigurado lang.