A baby should be off the bottle or at least trying to use a cup by age 1 and no later than 18 months to 2 years of age.
You should start putting the babies milk or other drinks in a Sippy cup instead of the bottle by age 1 year so that the baby can start getting used to the sippy cup.
Then by age 18 months switch to a regular cup and by age 2 the child should be able to use a regular drinking cup by itself without little to no assistance.
Sometimes you have to force the issue but using a cup is an essential part of a child's life so it has to be done.
Your child can't drink from a baby bottle in school or other places when they grow up.