A few brick and mortar store retailers around South Africa have started asking "May/can I have your cellphone number?" when I'm making a purchase to which I respond with either "You don't need that." or simply "Nope.".

When asked why, conversation typically goes like:

Me: "I don't want my phone being sent SMSes or phone calls from your company or anyone they would share my number with."

Them: "Oh, don't worry, that won't happen from us."

Me: "Well it absolutely won't happen if you don't have my number.".