You need to instruct the lostik to use another spreading factor, how you do that depends on the software you are using. As you don’t provide any information on what that software might be (and I don’t want to spend time researching what might be available and next guess what you could be using) you need to find out how to do that yourself. As it seems the lostik is based on a microchip module I would start with the RN2483 commands manual from the microchip site,
Hint: you know what hardware and software you are using, we don’t know the details of every LoRaWAN device on the market so when asking a question please provide links to what you are using, that way we don’t have to google.
BTW, you are not sending data to a gateway, you are sending data to the network. If you are lucky there are multiple gateways in your vicinity receiving the transmission and forwarding it to the backend. LoRaWAN is not WiFi where you transmit data to a specific access point.