Phone scams are increasingly more common. This is why it is important not to hand over your phone number to too many different companies, as you don't know who else they will give your phone number to. Here are some general guidelines:
To block phone numbers on your iPhone, follow these steps:
Instructions for Samsung phones, can be found here. For other Android phones, you will have to check the user guide for your specific cell phone to find out how to block phone numbers.
Additionally, you can ask your carrier to do the blocking for you (for a fee). Click on your carrier below for more info: