Hi @AJ2403, welcome to our forum!
If you want to block calls you will need to use a third party application from the Google Play store as the Xperia E5 does not have any setting for blocking calls.
You can however save the number as a contact and change a setting so all calls from that number goes directly to your voicemail.
- Find and tap Contacts.
- Tap the contact that you want to forward to voicemail, then tap the Edit contact icon (icon with a contact and a pen).
- Tap the menu button (three vertical dots), then mark the All calls to voicemail checkbox.
- Tap Done / SAVE.
Let me know if that helps! 
