I have an iPhone 7plus iOS10.3.3. One of my contacts, the phone insists on sending a text message to their landline rather than the mobile

I have an iPhone 7plus iOS10.3.3. One of my contacts, the phone insists on sending a text message to their landline rather than the mobile! - 1

Wow that's weird

Delete the contact number, shut down the phone, call the number and try to save as contact again.

I have removed the landline number from the contact and popped it in the notes, so the only option is to now send a text to the mobile and it still does it! Maybe i will try deleting all the previous messages and send another?

I don't see how the phone could insist on anything. You are the one that has it do anything, including of course putting a phone number to text someone with.