How did a scammer get my iphone number?? [View all]

I received a text message today (supposedly from USPS) saying a book I ordered is being held due to a faulty
address and would I please go to (link) to remedy the problem.

It was a scram, for sure-- but I couldn't help wondering how those people got my iphone number
and
Is my iphone in danger of being hacked?

If so, is there a program that could go through and delete any nefarious items?

Thank you