is baby using only 1 type bottle or variety bottle? I tried with tommee tippee and my boy choked. so I stick to 1 model only. at that time was using Philips avent. then secondly, try to "play" / "talk" to baby when feeding. just to prevent them getting bored of sucking.. can try tapping the bottle with the cap.. for burping.. If baby don't want to sit. try to lay baby on lap, belly.. sometimes maybe baby might feel bloated and refused to drink milk. so can do some baby leg exercise or can apply baby oil / Ruyi oil and do gentle tummy massage. this will help to expel wind And help in digestion. :) hope it helps :)
https://sg.theasianparent.com/choosing-the-best-bottle-feeding-nipples-for-baby