Why can blocked numbers still leave voicemail on iPhone?

I’ve noticed that even when I block someone’s number, they can still leave a voicemail. The core of this issue is that phone call blocking on iPhones only restricts calls from reaching your iPhone directly. Once a call is diverted to voicemail, it leaves the network your phone controls and enters the domain of your cellular service provider. Since voicemail is managed at the carrier level, blocking a number doesn’t affect this service. The caller, being unaware of the block, leaves a voicemail, and your carrier stores it for you to retrieve whenever you choose. Think of it as two separate layers of filtering, with the block applying to one and the voicemail falling into another.

Blocking a number on an iPhone mainly stops the immediate disruption of a call or text, rather than preventing communication entirely. When you block someone, iOS directs their call straight to your voicemail. The caller won’t realize they’ve been blocked—except that you never pick up—and they can still leave a voicemail like any other unblocked caller would. Apple designed the feature this way likely to avoid confrontation or repeated attempts to contact users through other means. Consequently, it means the blocked person can leave messages, which you can listen to (or not) at your leisure without your phone ringing in the first place.

In my experience as a telecommunication engineer, the blocking feature on your iPhone pertains only to real-time call prevention. When a number is blocked, it essentially bypasses the call process and diverts it to voicemail directly. This way, the phone itself does not ring, and there is no immediate notification of an attempt. The voicemail system, however, operates separately and is not subject to the same user-level block settings. Voicemails are part of the carrier’s service infrastructure and are not controlled by the phone’s internal mechanisms. This separation ensures that voicemails can still be processed and stored regardless of a block on the receiving end.

The reason blocked numbers can still leave voicemail on an iPhone lies in how the blocking feature works on a technical level. When you block a number, your iPhone prevents calls and messages from those contacts from reaching your device. However, the call itself is still processed by your carrier network, not your device. As such, the blocked call is diverted to your voicemail as usual. This allows the blocked number to leave a voicemail because the blocking mechanism does not extend to the voicemail system managed by your carrier.

I found out that when you block a number on iPhone, the call is simply redirected to voicemail because the blocking functionality doesn’t extend to the carrier’s voicemail system. The iPhone’s call blocking works by telling your phone to ignore incoming calls and texts from the blocked number. The voice mails are handled by your carrier’s system and are processed as any other call would be if you didn’t answer. The blocked contact gets shunted to voicemail since your phone declines the call, but they can still leave messages as if it were any unanswered call. This separation between phone actions and carrier voicemail functions explains the issue fully.

From my understanding, when you block a number on your iPhone, the block applies directly to the phone’s interface. Your phone will not notify you of incoming calls or texts from that number; however, this does not prevent the caller from routing their call to your voicemail. The voicemail system is managed by your carrier, independent of your iPhone’s settings. Voicemails are stored externally on your carrier’s server, which your phone later accesses. Because of this separation, the block does not interfere with the voicemail functionality managed by your carrier. It’s a limitation of the system architecture, not something that can be modified easily from your iPhone alone.