A method ensures that data is not lost during an inter-Routing Area or inter-Network Service Entity cell change in a GPRS network. When a mobile station passes from one cell into another, a command is sent from the SGSN to the BSS serving the first cell, causing that BSS to discard any data awaiting transmission to the mobile station. A reply is sent from the BSS to the SGSN, and, in response thereto, the SGSN transmits data to the BSS serving the new cell, in order to ensure that all of the data intended for the mobile station is transmitted thereto.