Processing signalling relating to a telephony session. A first telephony session establishment request relating to the telephony session is received. The first telephony session establishment request comprises a first telephony identifier as a calling party identifier. The first telephony identifier is replaced with a second telephony identifier. The second telephony identifier is different from the first telephony identifier. Call processing relating to the telephony session is enabled to be performed based on the second telephony identifier. The second telephony identifier is replaced with a telephony identifier other than the second telephony identifier. A second telephony session establishment request relating to the telephony session is transmitted. The second telephony session establishment request comprises the other telephony identifier.