Users of national mobile networks (GSM or UMTS) in areas near the border between Portugal and Spain can occasionally enter into involuntary cross-border roaming while using their mobile phone (or other mobile equipment) to make or receive voice calls, video telephony, to send SMS or MMS or to access the Internet.
In such cases, when using mobile equipment in border areas, users may be charged prices applicable to the use of the service in roaming which, as a rule, are significantly higher than those applicable at a national level, particularly in the case of Internet access and SMS. In the case of voice communications, users will not only be charged more for the calls which they originate, but will also face charges for calls which they receive.
This may be due to several factors, including occasional problems of operator coverage (orography of the land) or momentary or temporary failure of the operator's network. However, because it is impossible to prevent involuntary roaming from occurring, users should be aware that this can happen and take measures to avoid it.
Activation of roaming can be detected through the identification of foreign operator's network and their welcome messages or messages giving details on roaming tariffs which the national operator is required to send when a user begins roaming. To avoid involuntary roaming, users should find out from their operator whether roaming is active on their subscription and how this service can be turned off, permanently or temporarily, or how they can select the network of the national operator manually.
However, occurrences of involuntary roaming are relatively rare and ANACOM, together with the Spanish regulator and national operators, have taken steps in terms of spectrum management that have significantly mitigated this problem.
