Went through exactly the same thing. I upsized the teat and had to retrain my baby to drink. The bottle training was very tough. She was really strong willed and physically strong too. A parentcraft nurse taught me to hold the botte with my first 2 fingers and rest the other 3 under her jaw. Then after inserting the bottle into the mouth, I would use the 3 fingers to close her jaw in a rhythmic way to encourage her to suck. The other thing that I was taught, especially if she was cranky and tired but not drinking, was to swaddle her, pat her to sleep on her side, then when she was very drowsy, to insert the bottle into her mouth. She was more willing to drink then. The biggest tip is that.. I could not be the one feeding her with the bottle. She wanted to latch, not take the bottle. So my husband had to be the one giving her the bottle, and it had to be at a different place from where I usually fed her.
Honestly, I struggled with bottle rejection with my baby time and again for about 10 months. I think only when we made her use the bottle for almost every feed during the day, did she finally give in and drink more.