Should I Call or Go to the Immigration Office on My Under Consideration Stamp Date?

Just GO to the immigration office on the date the under consideration stamp expires in your passport.

The reason some people said they called is because they deal with smaller satellite immigration offices who send the applications to their division office to get approved and sometimes they don't come back in the 30 days.

Chaengwattana is the main office for Bangkok so you just show up on that date.