My husband has been texting his girlfriend,he says he isn't doing them. Can someone hack his cell to do this?

I checked the properties on the email itself and it shows it comes from voice mail, but its addressed to his girlfriend. I know there is spoof card program where you call someone from your cell but show someone else's number instead of yours. So how does this work with texts. A disgruntled ex employee is trying to get a current female employee fired because she may have had a part in firing by making me (wife suspicious of a possible affair) which I may feel is true.