Article: If you're interested in blocking calls from salespeople and other spam calls, register for the National Do Not Call List. Registering is fairly simple. You just enter your number and e-mail. You should get an e-mail within 72 hours with instructions on how to complete your registration. If you want to block certain from a number of phones and electronic devices, consider getting a Google Voice account. A Google Voice account will keep all your numbers and contacts in one account. You can easily block numbers through Google Voice.  You can sign up for Google Voice for free if you live in the US. Log into your Google Voice account and find the number you want to block.  Select the check box next to the number. Hit "block." This will block this person from contacting you on any phones or electronic devices hooked up to your Google Voice account. Not all android phones have specific tech you can use to block calls. However, Android offers many free or cheap apps that can be used to block numbers.  Mr. Caller allows you to block calls and texts from specific numbers. It also allows you to automatically block unknown callers and block numbers from specific area codes. Truecaller is an app that can detect and weed out spam calls. It also allows you to block specific numbers. There are many free apps on the app store that can be used to block calls. Browse apps and read reviews to find an app that works for your needs.

What is a summary?
Register for the National Do Not Call List. Use Google voice to block certain numbers from any device. Use phone apps for Android.