The term ghost roaming is used to denote the transfer of small amounts of data through a foreign or other third-party mobile network which can occur even when data transmission is disabled on a mobile device. This is caused by a flaw in the 4G/LTE standard for mobile communications.
Ghost roaming and Swiss mobile service providers
Most Swiss telecom service providers do not pass on charges incurred through the unwanted transmission of data to their customers. Salt is an exception to this rule, as it regularly passes on ghost roaming charges to its customers.
Mobile device users who purchase data roaming bundles or options ahead of traveling are not normally affected by ghost roaming. The amounts of data transferred for the purpose of maintaining a data roaming link are typically so small that the cost is negligible.
Consider carefully reviewing your phone bills after traveling abroad to find out whether you are being charged for ghost roaming. If you notice data roaming charges even though mobile data was disabled, consider contacting your mobile service provider and inquiring about these charges. Typically, mobile service providers will remove this charge from your phone bill.
Interactive roaming calculator