Analogue of Roistat, Comagic - replace with GA + promotional code?

Question

Google Analytics

The task is to use the promo code from the site, which the user calls by phone, to find out the source of his first visit, which could have been a week ago. + See the history of visits and page views.
Is there a way to implement this through google analytics or i.metrica?

Answer 1

And it’s not easier for you to make a replacement number
Organika-1
Context-2
Everything is clear with partners
The history of visits and views is already in analytics and metrics

Answer 2

You can enter the promo code (if it is really unique) into user variables via setCustomVar.