My husbands had texts from a female friend and she has phoned him abroad.what would you do ?

she is the wife of one of his oldest friends.she has called him in dubai and was asked by his firm to stop doing so-he has recieved further texts and i discovered this by asking an innocent question-he said" Oh youve looked at my phone ! then" i deleted it" I asked him what they talk about, about he said "work" nothing else.He got her the job recently(but i think they would call each other before that happened) i asked him to tell her to stop texting and calling 2 days ago. he said he would. he said she said "no problem" but i checked his phone and they had a half hour conversation,Shall I call her to find out her side of the story?im on the brink of doing so, would it be a bad idea ? any personal experience of this situation ?i feel there is more to this .we have been married 10 years.