In 2001-2002, Greece moved to a closed ten-digit numbering scheme in two stages, with the result that subscribers' numbers changed twice. For example, before the change, a number in Athens would have been dialed as follows: xxx xxxx (within Athens) (01) xxx xxxx (within Greece) +30 1 xxx xxxx (outside Greece) In 2001, a '0' was added after the area code, which was incorporated into the subscriber's number: 01 0xxx xxxx (within Greece, including Athens) +30 1 0xxx xxxx (outside Greece) Finally, in 2002, the leading '0' was changed to a '2' (for geographic numbers) : 21 0xxx xxxx (within Greece, including Athens) +30 21 0xxx xxxx (outside Greece) Mobile phone numbers were similarly prefixed with the digit '6'. Note that because of number portability, for both geographical and non-geographical (mobile, toll-free, premium rate) numbers, one cannot be sure about the operator that a number belongs to. Thus, for geographical numbers, one cannot be sure that a subscriber number that starts with a 0 is operated by OTE or that a toll free number that starts with 800-11 is operated by OTE. Also for mobile networks one cannot say for sure that a number that starts with a 69x actually belongs to the mobile carrier to which it was assigned.