A method for shifting an original call established between a first user device (1) and at least a correspondent device (2) through a first application server (3) in order to route it through a second application server (4), the method comprising—instructing the first application server (1) to forward the original call through the second application server (4) to the first user device (1) upon receiving the application server shift instruction, the first application server being instructed to establish a three-way conference communication between the first user device (1), the correspondent device (2) and the second application server (4) in order to forward the original call from the first application server (3) to the second application server (4); —determining that an incoming call routed from the second application server (4) to the first user device (1) has an identification information matches identification information of the original call; —causing the first user device (1) to pick-up the incoming call routed from the second application server (4) to the first user device (1) and instructing to release the call branch between the first application server (3) and the first user device (1) upon determining that the identification information matches.