That only works if the marketing campaign exclusively uses the number you're blocking. In some cases - for example, political SMS in the US - it turns into whack-a-mole unless you unsubscribe properly.
Yep, US political spam is unblockable. I receive “wait, you’re a Republican, this can’t be right‽” style SMS messages from 10–20 unique phone numbers every day. The FCC’s spam complaint form only accepts one sender number per submission so I’m about 1,300 complaints in so far.
