What times/days do Muslims pray?

My SO is Muslim and I'm Chrisitian. I want to be able to call him/text him and not distrupt his prayer time. Sometimes I call and he's at the Mosque and I get disappointed with myself because it should be a time when he prays but yet he picks up my calls/ replies to my text...I respect his religion and I also respect that he takes his time of his busy life to pray to Allah/God