Credit Shield
Generate a late-fee waiver / goodwill removal letter and set an automatic monthly reminder (.ics works in Apple Calendar, Fantastical, Google, Outlook).
1) Late-Fee Waiver / Goodwill Letter
Attach your payment confirmation screenshot when you contact the issuer.
2) Monthly Payment Reminder (.ics)
Repeats monthly; includes VALARM. Times are written in UTC so Apple/Fantastical/Google interpret them correctly.