We estimate the Bit Error Rate for a hybrid network composed by a classical network working together to a Quantum-Key-Distribution-based (QKD) network, for the concrete scenario of Internet of Things networking. Essentially we performs calculations of the probability of success call completion (PSCC) in the case where a high user mobility is performing e-banking by which is assumed that the end user requires a high confidence to carry out transactions without any risk to be monitor by external hackers or eavesdroppers. It clearly requires to achieve handover by using both classical and quantum key distribution (QKD) networks resources. We follow the fundamental sequence established by (i) probability for requesting a cell in the nearest Base Station (BS), (ii) probability for engaging a IoT network during the hysteresis time, (iii) probability of being not blocked due to a high number of calls requests given by the services that offers a IoT network, and (iv) probability for being engaging again to a BS. We assume that the QKD network oveys the scheme based on the Bennett-Brassard protocol (BB84) by guaranteing a high QKD hardware efficiencies.