Network Function Virtualization (NFV) is deemed as a mean to simplify deployment and management of network andtelecommunication services. With wireless access networks, NFV has to take into account the radio resources at wireless nodes inorder to provide an end-to-end optimal virtual network function (VNF) allocation. This topic has been well-studied in existingliterature, however, the effects of variations of networks over time have not been addressed yet. In this paper, we provide a model ofthe adaptive and dynamic VNF allocation problem considering VNF migration. Then we formulate the optimisation problem asan Integer Linear Programming (ILP) and provide a heuristic algorithm for allocating multiple service function chains (SFCs).The proposed approach allows SFCs to be reallocated so as to obtain the optimal solution over time. The results confirm thatthe proposed algorithm is able to optimize the network utilization while limiting the reallocation of VNFs which could interruptservices.