How do i block unwanted mobile numbers that call me on an iphone 4

Hello John
It depends wich phone you have and wich operating system it has..... in other words for Android smart phones see here :
https://www.androidauthority.com/how-to-block-a-phone-number-246484/
for Iphones look here :
https://www.macworld.co.uk/how-to/iphone/block-number-iphone-3457215/

and for normal phones you have to look on the settings for the number or call...
hope thats helps
good day to you

you can download a call blocker app from the app store

Then just add the numbers to that app

Go to the link
Block calls and block or filter messages on your iPhone iPad or iPod touch

here they show 4 ways to block numbers on an iPhone:
How to Block Number on the iPhone

Need to block a specific phone number from calling or texting your iPhone? It could be telemarketers, spam text messages, or that crank that won't stop calling and messaging. Apple's iOS does not have a built-in feature to block a phone number, but there are other solutions.

1. Your carrier might be able to block individual numbers. AT&T has an optional feature called Smart Limits for Wireless that runs $4.99 per month. One of the many functions is the capability to block up to 30 numbers from calling or texting your iPhone.

Verizon Wireless offers Spam Control for no additional charge. This feature can be found under My Services when logged into your account, and blocks up to 5 numbers from calling or texting.

2. Owners of jailbroken iPhones can install apps from the Cydia Store that will block phone numbers.iBlacklist is fully compatible with all iOS devices, iOS 5 and older firmware. For a one-time cost of $12, iBlacklist adds a plethora of useful features to your iPhone including the ability to block calls and texts from individual numbers.

MobileLog is currently in development and will be offered for sale to jailbroken iPhone owners soon. The app will also provide many enhancements to the stock calling app as well as number blocking.

3. Make sure you've registered your iPhone number with the National Do Not Call Registry. This will not stop texts, but it will require most telemarketers to stop calling your line within 31 days. Complaints can also be filed using the same website, and phone number registrations with the service never expire.

4. Assign a silent ringtone to the numbers you don't want to answer. This stops calls from bothering you, but texts will still sound an alert.

5. Another calling only solution are services such as TrapCall, which has plans starting at $4.95 per month. No iPhone app installation is required, and once you're signed up TrapCall will unmask blocked caller IDs and blacklist unwanted callers. More expensive plans can be purchased that offer more in-depth functions.

Hi
PUK code is called as PERSONNAL UNBLOCKING KEY.
Your phone will ask for PUK code when you entered the PIN code wrongly several times depending upon the mobile make. The mobile asks for PUK code so that unauthorized persons do not use your mobile for wrong cause.
To get PUK code please contact your service provider through phone or go directly to their office. They will provide you the PUK code for your mobile. The PUK code for mobile phone.so that you can open your phone. When you planning to call your service provider you cannot use your mobile as it is fully locked. Please use some other mobile with same network to call your service provider.
While you get the PUK code ,the service provider customer care officer will ask for your personal details to check whether the mobile belongs to you only. If they are satisfied with your answers they will provide with the PUK code
DONOT enter the PUK code several times wrongly,It will block your sim card permanently.
This PUK code is FREE. You no need to pay any sum to get the PUK code
Thank You.

Can no be done. Iphone doesn't have a 'black list' for phone numbers

Find your solution from the list,
Apple Iphone Smartphone
Codes:

• Unlock Code,
• Password,
• Puk Code,
• Lock Code,
• Other Codes.

Software & Hardware Problems

• Software Problems (Hang, Youtube etc.)
• Hardware Problems (Display, Charging etc.)

Find Solutions for other Apple Products:
Apple Iphone 3G
Apple iPod Touch Digital Media Player

I think there is no option in your phone for it but If you have the cell phone number, call your cell service provider and tell them the number you want to block. If its an unknown number, there is no real way to block it.

HOW CAN I BLOCK LIST UNWANTED NUMBER FOR MY MOBILE PHONE