MY HUSBAND SOMETIMES PICKS HIS CALLS WHEN WE’RE HAVING SEX

My husband is in the habit of picking his calls when we are having sex. He would pick his phone & actually talk into it while he's pumping away. I find it so annoying. I've told him severally to stop but he says it's not a big deal. His voice is usually coordinated when he's talking on the phone during sex, I don't know how he does it but how can I get him to stop? PLEASE I NEED YOU ADVICE