Seven Secret Codes That Let You Access Hidden Features On Your iPhone

5. Call Barring.
With call barring, you can block both incoming and outgoing calls. You have to pay for the service, but if you do, you can enable call barring by entering *33*PIN# or disable it by entering #33*PIN#.
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6. Call Waiting.
Again, you have to pay for the service, but you can turn call waiting on and off — and figure out whether it’s on or off — with a few codes. Dial *#43# and “call” to find out the status of your call waiting. To turn it on, dial *43# and “call”, and to turn it off, dial #43# and “call.”
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7. Call Forwarding
Check to see if you’re forwarding calls, and where you’re forwarding them to, by entering *#21#.
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