This paper proposes a novel approach to call admission control (CAC) in adaptive wireless networks, called Semi-Adaptive CAC (SA-CAC). When a new or handoff call comes, the bandwidth allocated to the call can be adjusted according to the load of the network cell. Once the call is admitted, its allocated bandwidth is never adjusted throughout its lifetime. Therefore it will not lead to delay and overload of message transition and processing caused by degradation and upgrades, however it still maintains the advantages of flexible bandwidth allocation. We adopt one form of NeuroEvolution algorithm to learn good SA-CAC policies. The numerical results demonstrate that the proposed scheme is capable of maintaining the upper bounds of call blocking rate (CBR) and handoff failure rate (CDR), as well as increasing the network utility compares with traditional threshold based CAC scheme.