An anonymous caller or someone with a blocked number is hiding their name and details. If you often receive anonymous calls, there are ways to unmask the caller and call him back or block his number. This can be done by contacting your provider or using special smartphone apps.
Steps
Method 1 of 2: Call back blocked numbers using your home phone
Step 1. Check if you can call people back automatically
This can be done with some telephones by entering a specific code.

Step 2. Lift the handset
Enter the code that corresponds to your telephone or provider.

Step #3. Wait for the connection to be established
If you are unable to call someone back, you will receive an automatic message explaining what the problem is.

Step 4. Ask the person on the line for their phone number
If it's an advertising service, ask to be included on their "Don't call again" list.

Step 5. Consider blocking anonymous callers by default
You can request this from some providers for a monthly fee. This way you will never again be bothered by stalkers or telephone exchanges.
Step 6. If you are being harassed by phone, call the police
Sometimes the police can find out who the caller is and possibly arrest this person or impose a fine.
Method 2 of 2: Call back blocked numbers using your smartphone

Step 1. Go to the app store on your iPhone or the Google Play store on your Android phone

Step 2. Search the app store for "TrapCall"

Step 3. Install TrapCall
The app is free for both Apple and Android phones.

Step 4. Open the app, agree to the terms and let the app do its job

Step 5. Subscribe to TrapCall
This also allows you to see their phone numbers for anonymous callers, after which you can call them back or block them.
- Sign up for a basic, premium, or ultimate subscription for $3.95, $7.95, and $19.95 per month. A subscription for 2 years is cheaper.
- Monthly base, premium and ultimate subscriptions are available for $4.95, $9.95 and $24.95.

Step 6. Wait for an anonymous caller to call you
Reject the caller by pressing the red button.

Step 7. Wait for the call to be processed by TrapCall
Within a few seconds you will see the number appear on your phone.