That is another idea… He could call and say, “Sorry, Auntie, I was unable to meet you. I have a business trip, have to go to London for (explain the job a little bit). But inshAllah, I’d love to meet you soon.” If he’s respectful like that, it could leave a good impression…
BUT, the thing is the mom has hung up before on confused kuri, she could hang up on him. The mother won’t see him in person, so she might be braver to put him down over the phone… tell him she’s not interested in meeting him, stay away from her daughter, etc… then the dial tone (she hung up). If mom does that, the guy might be really hurt and could reconsider the relationship.