Hi @Willie16; welcome to our Community and sorry to hear about this.
As you've followed the correct steps to do this, I'd suggest contacting our support team so we can assist further.
To do this, open an incognito window without logging into any account and when onthis page, click on the 'Need help with a billing issue?' button and submit a Help Request from the relevant option at the bottom of the page and input the email address connected to the Dell promotion you're trying to apply and wait for our e-mail.
I hope this helps and please let me know if you have any more questions Willie.