Supplier for Automatic Weather Station Modems and SIM Cards

We operate a network of approximately 300 automatic weather stations (AWS) located primarily in the UK with some international sites. Each station collects real-time weather observation data on an onsite logger and transmits it to our cloud-based central system every minute. Our sites have varying infrastructure: some have mains power while others operate on 50W solar panels; the majority use 4G connectivity with a subset currently limited to 2G connectivity. We are seeking a supplier to provide modems and SIM cards to enable reliable, real-time transfer of land surface observation data from all sites to our central cloud collection system every minute. Suppliers should have experience supporting mixed-generation mobile networks (2G and 4G), low-power environments, and remote locations.