Is there anything he can do if the mother won’t let the father talk or see his daughter even if he pays support?

My boyfriend pays child support. He calls and texts his children’s mothers asking when can he see or talk to his children. His daughter’s mom tells him a day he can. When that day comes, he calls and calls and calls but no answer. He has seen his daughter at a local gas station and she was so happy to see him. Her mother yelled at her for talking to her dad. Please help.