The following operators abolished roaming charges before 15 June 2017: we have published our final decision to maintain the power to regulate national mobile roaming if necessary in the future. We believe that regulation remains an important competitive security, especially in view of 5G networks and potential new entrants on the horizon. In Russia, even domestic operators charge different rates depending on whether users are inside or outside their “region of origin”. A number of legislative attempts to remove “internal roaming” have failed due to opposition from operators.  Following the annexation of Crimea in 2014, Russian operators face considerable criticism, as they do not offer their services directly in Crimea, although it is formally recognized as a regular federal subject within Russia.  In the UK, major network operators typically send text notifications to inform users that they are now charged international tariffs, making it clear when this will apply. Data roaming charges abroad vary depending on the type of telephone agreement (pay-as-you-go or monthly contracts). Some carriers, including T-Mobile and Virgin Mobile, do not allow customers to use international roaming without pre-emption of an international add-on or bolt-on.  This is the case, for example, when a roaming mobile phone is called. Although these user/network scenarios focus on roaming from GSM network operator networks, roaming can be clearly bidirectional, i.e.
from public Wi-Fi operators to GSM networks. Traditional roaming on networks of the same standards, for example.B. from a Wi-Fi connection to a Wi-Fi connection or to a GSM network to a GSM network, has already been described above and is also defined by the strangeness of the network depending on the nature of the entry in the participant register. The example of WIFI/GSM roaming makes it possible to distinguish the following scenarios (see GSM Permanent Association reference document AA.39): this type of roaming concerns the possibility of switching to the network of a foreign service provider. It is therefore of particular interest to international tourists and business travelers. Overall, international roaming is the easiest with the GSM standard, since it is used by more than 80% of mobile operators worldwide. But even in this case there may be problems, since countries have allocated different frequency bands for GSM communications (there are two groups of countries: most gsm countries use 900/1800 MHz, but the United States and other countries in the United States have allocated 850/1900 MHz): for a phone to work in a country with a different frequency allocation, it must support one or both frequencies of that country and therefore sort or quadri-band. . . .