When I queried this mobile number 07958879879 (not known to me)with VM earlier in the year, they informed me when abroad it depends on the 3rd party network that you are connected to when making calls or texts from abroad and this is why the correct number does not appear.
I have contacted EE, Orange and Vodaphone and they have informed me in writing that when they produce mobile bills , it does not matter which country you are staying their bills will always show the correct numbers that you have contacted.
Earlier in the year I complained to VM and then after 3 months they managed to produce a correct bill with the correct mobile numbers, they assured me this would not happen next time I went on holidays. Well I have just come back from Turkey and once again the number 07958879879 is currently appearing on my bill. How is one supposed to check your account if a number that you have no knowledge of appears on your mobile bill? Anybody else having a problem with this number?