Paramount+ on Us Upgrades?

I have the same problem with streaming promotions--most don't allow you to keep the lower essential cost and simply add on the commercial-free plan.  I can't stand commercials and refuse to watch them.  Peacock, however, allowed for it to be done.  I'm paying $1.99 for the basic plan, instead of $4.99, and have the no-commercial plan for $4.99 added on to the $1.99. (The Peacock promotion wasn't through T-Mobile, however, as far as I remember.)