Local number portability - telephone number portability for land-line users
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Mobile number portability - telephone number portability for mobile phone users
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Toll-free number portability - telephone number portability for freephone subscribers.
telephone | Telephone tapping | Plain old telephone service | Nippon Telegraph and Telephone | Lucky Number Slevin | Reynolds number | Mach number | serial number | Random number generation | International Standard Book Number | prime number | Personal identification number | number | Two in a Million/You're My Number One | Telephone exchange | telephone exchange | Social Security number | Rikki Don't Lose That Number | Prime number | Premium-rate telephone number | Jackass Number Two | The Bell Telephone Hour | Telephone switchboard | Telephone company | Telephone | Software portability | Opus number | Number Girl | List of WTA number 1 ranked players | Lah number |