For quick access to troubleshooting, settings, or information about your cell phone bill, your iPhone supports some common call codes. We introduce some of the most helpful codes to you.
We informed you last fall about Apple’s iPhone Signal Strength Placebo, a code for the iPhone that aids in the identification of 3G network connectivity issues with AT&T.
Your iPhone does a field test when you enter *3001#123456#* and tap “Call,” and the results might be used, for example, to determine signal strength. (It also provides a ton of additional information that, unless you happen to be a cellular engineer, is probably beyond your comprehension.)
Although the most helpful code for the iPhone is the one shown above, there are several more intriguing codes.
What *#33# means on iPhone
By checking all the usual suspects (voice, data, fax, SMS, etc.) to determine whether barring is enabled or disabled for outgoing, dialling *#33# and tapping Call checks for call control bars.