Someone put the number in her phone.

She isn’t sure how to navigate through the contact to get the number.

Something I learned as I got older and has drastically improved my relationships is to just answer the question as asked.

Grandma writes down her grandkids numbers into her address book that she's used for many decades. It worked when she had a rotary phone, it worked when she had a cordless phone and it still works when she has an iPhone. If she ever decides to get some other brand of phone she will have no problem calling her gandkids because she has a system that works independently of whatever new technology comes around.

Meanwhile her grandchild will find it difficult to adapt to a phone from another company because they'll have to figure out how to export their contacts and import it into the phone, and then adapt to a different interface. They will likely just continue use phones from Apple no matter how much the charge for them, regardless of their reliability or quality. Too much hassle to change.

Now it's debatable which way of using the phone is better, but there are some real advantages to how grandma does it.

So just give her the damn number, so she can write it in her address book and she can dial in that number when she wants to call you. Her way of using a phone is not necessarily worse than your way of using it.

GIVE HER THE NUMBER

My 86 year old mother refuses to learn to use a smart phone, and still doesn't know how to send or read texts.

There's a chance this grandma wiped grandchild's butt when grandchild was a baby. Perhaps also tried to catch the occasional random baby puke in her hands, instead of letting it spill on the floor. Or on someone else's car seat. Grandchild should have just typed those numbers in.

iMessage works on emails too, maybe if this were an sms