COSMOTE informs its subscribers in border areas that they might registered with foreign networks. the registration with foreign networks entails increased charges for the subscribers as this category of calls are rated as international roaming calls.For this reason COSMOTE recommends to its subscribers in border areas, in order to avoid possible registration with foreign networks, to select COSMOTE network manually according to the instructions that are included in the manual of their handset.
http://www.cosmote.gr/cosmoportal/page/T60/section/Affiliate_Networks_Countries_Postpaid
http://www.cosmote.gr/cosmoportal/page/T60/section/Affiliate_Networks_Countries_CC