How do I get rid of unwanted calls and texts?

The first person that comes up with a general way to do that should get a Nobel Prize.

Other than that see if your carrier has an app that can block phone spam and texts. Also, for texts, forward them to 7726 (SPAM) so your carrier can monitor and blacklist offenders.

There are also 3rd party apps; the best-known (and probably still the best) is nomorobo from the app store. It is not free for iPhones (but is for landlines); it has a small monthly charge.

See the Apple articles below: 

Block phone numbers, contacts, and emails on your iPhone, iPad, or iPod touch

Block phone numbers, contacts, and emails on your iPhone or iPad - Apple Support

Avoid unwanted calls on iPhone -> Avoid unwanted calls on iPhone – Apple Support (UK)

Detect and block spam phone calls -> Detect and block spam phone calls - Apple Support

Block unwanted callers in FaceTime on iPhone

Block unwanted callers in FaceTime on iPhone – Apple Support (UK)

Answer or decline incoming calls on iPhone -> Answer or decline incoming calls on iPhone – Apple Support (UK)

For phone calls, see the following Apple Support article for information on silencing phone calls that are from callers you don't know: Detect and block spam phone calls - Apple Support