My son refused a dummy in favour of his thumb until 5 months, I desperately tried to break the habit due to what I heard about damaging teeth etc. I think part of the problem was the dummy I had selected to try him on was just whatever we were given at the hospital. I ended up trying countless dummies and found that he preferred the shape of the Avent silicon. Also whenever I noticed him putting his thumb in his mouth I simply said nothing but removed it, placed the dummy in and gave him a toy instead. Try different dummies and distraction. It worked for me.

i had a thumb sucker and found the more i mentioend it, the more she sucked. after a while i tried giving her things like puzzles and duplo to keep her hands busy and it worked a treat

How old is your baby? It is better to give a baby a dummy. As he/she gets a little older you can restrict it to sleep time. At some point you will decide to wean your toddler off the dummy. You may have dramas for a few nights. If she is still having a day sleep it may/may not be good to try weaning one before the other. A friend of mine’ younger sister, as she got older actually sucked her middle 3 fingers, especially in her sleep even after she gave up the habit during the day. If one of them woke up during the night they checked her and took them out of her mouth. If somebody else got up later they did the same thing.
She actually pushed her teeth out of shape and her jaw out of alignment. She noit only had to have braces on her teeth, she also had to wear a frame around her jaw for a little while. I’m not sure what the latest treatment is now as it was about 45 years ago.

My old boss a dentist always said to parents better a dummy than a thumb. A dummy (preferably an orthodontic one) can be taken away from a child but a thumb can’t!