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Easy method (requires root)
Yes, there is an app for exactly that and much more called 'GravityBox' (it is an Xposed module).

For information on how to install it, view a similar post here

Alternatively (does not require root)
If you are lucky your Phone app should have a "Blacklist" to which you can add numbers and prevent calls and/or messages (notifications) from them. Normally found in the settings of your default phone app...
If you don't have it, then you could even try a 3rd party phone app that will replace your default phone app that will do the trick (There is a large variety that are more beautiful, simplistic, up-front and have features including black-listing options...).
Using a 3rd party phone app will leave all your contacts intact, but you may loose your speed dial settings.

Easy method (requires root)
Yes, there is an app for exactly that and much more called 'GravityBox' (it is an Xposed module).

For information on how to install it, view a similar post here

Alternatively (does not require root)
If you are lucky your Phone app should have a "Blacklist" to which you can add numbers and prevent calls and/or messages (notifications) from them. Normally found in the settings of your default phone app...
If you don't have it, then you could even try a 3rd party phone app that will replace your default phone app that will do the trick (There is a large variety that are more beautiful, simplistic, up-front and have features including black-listing options...).
Using a 3rd party phone app will leave all your contacts intact, but you may loose your speed dial settings.

Yes, there is an app for exactly that and much more called 'GravityBox' (it is an Xposed module).

For information on how to install it, view a similar post here

Alternatively

If you are lucky your Phone app should have a "Blacklist" to which you can add numbers and prevent calls and/or messages (notifications) from them.

Easy method (requires root)
Yes, there is an app for exactly that and much more called 'GravityBox' (it is an Xposed module).

For information on how to install it, view a similar post here

Alternatively (does not require root)
If you are lucky your Phone app should have a "Blacklist" to which you can add numbers and prevent calls and/or messages (notifications) from them. Normally found in the settings of your default phone app...
If you don't have it, then you could even try a 3rd party phone app that will replace your default phone app that will do the trick (There is a large variety that are more beautiful, simplistic, up-front and have features including black-listing options...).
Using a 3rd party phone app will leave all your contacts intact, but you may loose your speed dial settings.

Yes, there is an app for exactly that and much more called 'GravityBox' (it is an Xposed module).

For information on how to install it, view a similar post here

Yes, there is an app for exactly that and much more called 'GravityBox' (it is an Xposed module).

For information on how to install it, view a similar post here

Alternatively

If you are lucky your Phone app should have a "Blacklist" to which you can add numbers and prevent calls and/or messages (notifications) from them.