If you're using LLV Validation on your phone number field, the following list of rejection codes could be useful in determining what is wrong or how it was accepted:
​
​110: Not Accepting Incoming Calls
​120: Phone Switched Off
​150: Assumed Mobile
​20: Number Dialled has not been recognised
​200: Call Barred
​21: Live
​24: Number Dialled has not been recognised
​25: Live
​28: Number unobtainable Tone or message
​29: Live
​300: Dead Number
​310: Allocated to non-BT provider, likely dead
​32: Network Congestion tone/message
​33: Live, Call rejected
​34: Ambiguous result - manual dial test required
​35: Changed Number announcement message
​38: Number Not available message
​40: Invalid telephone number dialled
​400: Bad Syntax
​42: Probably dead
​44: Long/short busy tone
​46: Temporarily Out of Service message
​47: Live
​50: Long/Short busy Tone
​500: Number Changed Message
​52: Ambiguous result - manual dial test required
​53: Ambiguous result - manual dial test required
​54: Badly formatted number
​55: Live
​57: Live
​58: Ambiguous result - manual dial test required
​59: Live
​600: Retry
​61: Live
​610: Number Unobtainable
​62: Long/Short Busy Tone
​620: Number Out Of Order
​63: Ambiguous result - manual dial test required
​630: Mobile Phone Temporarily Unavailable
​640: Network Congestion
​65: Live
​650: Temporary Equipment Failure
​660: Mobile Phone Temporarily Unavailable
​67: Live
​69: Live
​700: Unobtainable
​71: Live
​73: Live
​75: Live
API Problem
Client Rejected