A method, comprising: receiving, at a virtualizing gateway (105, 203), a first service request from a first user equipment, UE, (101, 201) via a first eNodeB (103, 202), wherein the first service request includes a first user identifier, wherein the virtualizing gateway is in communication with a first core network of a first mobile operator and a second core network of a second mobile operator, the first and the second network each including a serving gateway, SGW, (113, 114) and a packet data network gateway, PGW, (115, 116); receiving, at the virtualized gateway, a list of user identities that may be permitted to use the first core network or the second core network; applying, at the virtualizing gateway, a filter using the said list to the first user identifier of the first UE; forwarding, at the virtualizing gateway, based on the applied filter, the first service request from the first UE to the first core network; receiving, at the virtualizing gateway, via a second eNodeB (104, 202), a second service request from a second user equipment, UE, (102, 201), wherein the second service request includes a second user identifier; applying, at the virtualizing gateway, the filter using the said list to the second user identifier of the second UE; forwarding, at the virtualizing gateway, based on the applied filter, the second service request from the second UE to the second core network, wherein the virtualizing gateway is acting as a gateway between the first eNodeB and the first core network, and between the second eNodeB and the second core network, wherein the virtualizing gateway acts as a virtual eNodeB to the first and second core networks and acts as a Mobility Management Entity, MME, to UEs that connect, and wherein either of the first or the second eNodeBs provide access to either of the first and the second core networks; and synchronizing a configuration of the filter from a configuration server to the virtualizing gateway, wherein the configuration comprises at least the said list. receiving, at a virtualizing gateway (105, 203), a first service request from a first user equipment, UE, (101, 201) via a first eNodeB (103, 202), wherein the first service request includes a first user identifier, wherein the virtualizing gateway is in communication with a first core network of a first mobile operator and a second core network of a second mobile operator, the first and the second network each including a serving gateway, SGW, (113, 114) and a packet data network gateway, PGW, (115, 116); receiving, at the virtualized gateway, a list of user identities that may be permitted to use the first core network or the second core network; applying, at the virtualizing gateway, a filter using the said list to the first user identifier of the first UE; forwarding, at the virtualizing gateway, based on the applied filter, the first service request from the first UE to the first core network; receiving, at the virtualizing gateway, via a second eNodeB (104, 202), a second service request from a second user equipment, UE, (102, 201), wherein the second service request includes a second user identifier; applying, at the virtualizing gateway, the filter using the said list to the second user identifier of the second UE; forwarding, at the virtualizing gateway, based on the applied filter, the second service request from the second UE to the second core network, wherein the virtualizing gateway is acting as a gateway between the first eNodeB and the first core network, and between the second eNodeB and the second core network, wherein the virtualizing gateway acts as a virtual eNodeB to the first and second core networks and acts as a Mobility Management Entity, MME, to UEs that connect, and wherein either of the first or the second eNodeBs provide access to either of the first and the second core networks; and wherein the virtualizing gateway is acting as a gateway between the first eNodeB and the first core network, and between the second eNodeB and the second core network, wherein the virtualizing gateway acts as a virtual eNodeB to the first and second core networks and acts as a Mobility Management Entity, MME, to UEs that connect, and wherein either of the first or the second eNodeBs provide access to either of the first and the second core networks; and synchronizing a configuration of the filter from a configuration server to the virtualizing gateway, wherein the configuration comprises at least the said list.