You should be able to block any number from calling or texting you in your phone settings.
Apple official guide to blocking a number on iOS
Google official guide to blocking a number on Android
There are a few apps you can use to block numbers on your phone. Have a browse, compare a few, and pick the one that fits you best.
Blocking a number in your phone will not prevent the caller from leaving you a voicemail. You can only do that by dialling 1626, but that'll disable voicemail for all callers.
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