Name Typo on Amex application

[Gothbe]

Yesterday I was rushing to submit an application for the BA Amex 70k promotion. Just as I hit submit I noticed I’d left a letter out of my mums surname! At that point it was too late to do anything and the application was accepted! The surname does not tie up with her BA membership number. What is the best plan:
A. wait for the card to arrive and then contact Amex?
B. do the 3k spend, get the 70k bonus and then contact Amex
C. Contact Amex with the application reference and change it now. I’m worried that changing it now might lose the promotional sign up

[Carlos]

Ideally B however this may affect transactions in the process. So go with A