How do I block the number of a nuisance caller?

Call your carrier and ask them to block the number for you. Or you may use apps to help you block a number. If you are using an iPhone, you can directly block a number in the Phone app or go to Settings>Phone>Blocked>Add New and add the number you want to block to the Blocked List. Here's the detailed guide on that: How to Block Numbers on iPhone and Find Blocked Numbers on iPhone

When they ring u again. Store the number in your contacts! Then u can touch the end button on ya phone, and you will hang up on the caller, without talking to them at all

Android:

• From the call log, you can disable incoming calls from specific numbers.
• Select the number you want to block, then hit More or the 3-dot menu icon in the upper right corner and choose to Add to reject list.
• This will disable incoming calls from specific numbers.

1. To block someone already added to your iPhone's Contacts, go to Settings > Phone > Call Blocking and Identification > Block Contact.
2. To block a number that isn't saved as a contact in your phone, go to the Phone app > Recents.
3. Click the exclamation mark next to the number.
4. Scroll to the bottom and select Block this Caller.