Hi, I see this is an old post, but there are many similar request out there so here is a partial workaround, although a bit extensive.
Apple gives the option to block callers and texts, and from a callers perspective this would make it seem that the call went straight to voicemail, (and texts being sent) although nothing is cashed on the device and you would never be able to check who is disturbing you/how often as with voicemail.
If you for some reason only want a spesific person or group not to disturb you and also be able to check your treads and calls you can do the below:
The Do not Disturb function offers the option to Allow Calls From certain groups while activated, as Favorites, No One, etc. Although there is no native way to create new groups on the phone by yourself.
But there are plenty of apps that can sort contacts into groups that work with the native system. Groups is one example.
The extensive part is to create a new group that contain every contact in your adress book except the ones you want to go straight to voicemail. This could be a heavy manual job if you got a lot of contacts you want to recieve calls from.
When created, go to Settings > Do not Disturb > Enable Manual and Allow Calls From > choose your new group(s) and set silence to Always.
For texts it's a lot simpler as you only need to go to your spesific tread > Details and activate Do not Disturb for that tread.
And if you also do not want the sender getting read receipts for iMessages, go to Settings > Messages > and disable Send Read Receipts if this is activated.
What this achieves/pros:
- Able to send specific numbers directly to voicemail.
- You will see the call as a regular missed call the next time you access your phone.
- The caller will not know, in the same way the block function works.
- Texts will be silent but recieved as normal.
Cons:
- This also affects all unknow callers or people in your adress book where there are no phone number saved. (One of the pros depending how you look at it)
- You need to include new contacts to your group as you get them.
- Texts would still be in inbox.
- You have to stay in Do not Disturb mode always.
- A lot of hassle compared to just blocking the number.
I use IOS 8.3 - I do not know if this applies to older versions of IOS.
Hope this helps someone