A method for controlling a network capacity, operated by a mobile Network Operator Policy and Charging Rule Function, MNO-PCRF, the method comprising: receiving an instruction message for setting up an IP Connectivity Access network, IP-CAN, session for a User Equipment, UE, obtaining a UE identifier from the instruction message, and determining from the UE identifier a Mobile Virtual Network Operator, MVNO, serving the UE corresponding to the UE identifier; forwarding the IP-CAN session setup instruction message to a Policy and Charging Rule Function, PCRF, in the MVNO, MVNO-PCRF, the MVNO serving the UE; receiving an IP-CAN session setup acknowledgement message carrying a Policy and Charging Control, PCC, rule of the UE, sent by the MVNO-PCRF; and replying to a network element sending the instruction message, with the IP-CAN session setup acknowledgment message for the UE, upon determining according to the PCC rule of the UE that the MVNO serving the UE does not exceed a granted capacity of the MVNO; sending to the MVNO-PCRF an alert that the granted capacity of the MVNO serving the UE is exceeded, upon determining according to the PCC rule of the UE that the MVNO serving the UE exceeds the granted capacity of the MVNO; characterized in that, after the alert is sent to the MVNO-PCRF that the granted capacity of the MVNO serving the UE is exceeded, the method further comprises: starting a preset wait timer; if a new PCC rule of the UE sent from the MVNO-PCRF is received before the wait timer expires, then determining again according to the new PCC rule of the UE whether the MVNO serving the UE exceeds the granted capacity of the MVNO; and if no new PCC rule of the UE sent by the MVNO-PCRF is received before the wait timer expires, then replying to the network element sending the instruction message, with an IP-CAN session setup failure message for the UE. receiving an instruction message for setting up an IP Connectivity Access network, IP-CAN, session for a User Equipment, UE, obtaining a UE identifier from the instruction message, and determining from the UE identifier a Mobile Virtual Network Operator, MVNO, serving the UE corresponding to the UE identifier; forwarding the IP-CAN session setup instruction message to a Policy and Charging Rule Function, PCRF, in the MVNO, MVNO-PCRF, the MVNO serving the UE; receiving an IP-CAN session setup acknowledgement message carrying a Policy and Charging Control, PCC, rule of the UE, sent by the MVNO-PCRF; and replying to a network element sending the instruction message, with the IP-CAN session setup acknowledgment message for the UE, upon determining according to the PCC rule of the UE that the MVNO serving the UE does not exceed a granted capacity of the MVNO; sending to the MVNO-PCRF an alert that the granted capacity of the MVNO serving the UE is exceeded, upon determining according to the PCC rule of the UE that the MVNO serving the UE exceeds the granted capacity of the MVNO; characterized in that, after the alert is sent to the MVNO-PCRF that the granted capacity of the MVNO serving the UE is exceeded, the method further comprises: starting a preset wait timer; if a new PCC rule of the UE sent from the MVNO-PCRF is received before the wait timer expires, then determining again according to the new PCC rule of the UE whether the MVNO serving the UE exceeds the granted capacity of the MVNO; and if no new PCC rule of the UE sent by the MVNO-PCRF is received before the wait timer expires, then replying to the network element sending the instruction message, with an IP-CAN session setup failure message for the UE. starting a preset wait timer; if a new PCC rule of the UE sent from the MVNO-PCRF is received before the wait timer expires, then determining again according to the new PCC rule of the UE whether the MVNO serving the UE exceeds the granted capacity of the MVNO; and if no new PCC rule of the UE sent by the MVNO-PCRF is received before the wait timer expires, then replying to the network element sending the instruction message, with an IP-CAN session setup failure message for the UE.