My boyfriend is jealous of my ex-husband talking to his kids...

My boyfriend and I are expecting our baby girl in October... BF gets jealous if my ex-husband talks to my 2 children. BF says I should never answer the phone to the ex because no child support is paid. However, I have done some research on this... and Indiana law states that the custodial parent does not have a right to withold visits or communication based on non-payment of child support. What should I do?