So a "stopper" can also mean a plug (i.e., something you shove into the neck of a bottle or a pipe to stop things coming out). "Stop" can also then be a verb which means, "put a stopper into"; and "unstop" can mean "remove the stopper from".

Since (it sounds like) this is talking about blocking and unblocking the flow of messages from that number, using "UNSTOP" (remove the thing blocking it) makes more sense than "START"; particularly as the latter seems to imply that you're asking to immediately begin receiving messages, whereas the former simply means to no longer block the messages.

it's because of ungood design

START works as well. At least for numbers provided by twilio: https://help.twilio.com/articles/223134027-Twilio-support-fo...

There probably is a START instruction internally, but it won't take action against a number for which there has been a previous STOP. So UNSTOP acts like FORCE START.

Unfortunately, the world is opt-out, not opt-in.

Probably a Cisco engineer who built that