This paper presents a study on optimizing LoRaWAN network parameters, focusing on the configuration of end devices, network servers, and gateways to minimize transmission collisions. The study is based on a large-scale network deployed in Wrocław, Poland, a city with a population of approximately 900,000 residents. The network connects over 40,000 devices installed in challenging environments, including basements, sewer manholes, and other subterranean locations, with coverage provided by more than 120 gateways. The primary objective is to achieve a Service Level Agreement (SLA) ratio approaching 100%, defined as the ratio of successfully transmitted messages by unique devices to total devices over a specified period, such as a day or week. The paper emphasizes minimizing transmission losses, particularly given that each device transmits messages only a few times daily. Our research highlights a methodology for periodically adjusting channel configurations based on environmental conditions as the key factor in optimizing the SLA. The findings suggest that successfully applying these adjustments, particularly with regard to the channel plan, is crucial to achieving the desired network performance.