A computer system comprises a memory, a cellular telephony communications device configured for sending and receiving cellular text messages, and a processor coupled with the memory and the cellular telephony communications device. The processor is configured to: receive, via the cellular telephony communications device, a cellular text message sent from a cellular telephone of an accessing entity, wherein the cellular text message includes a cellular telephone number of the cellular telephone, an instruction regarding reward points, and an image file; use the cellular telephone number to identify a reward program account; extract an authentication token embedded in data of the image file; authenticate access to the reward program account based upon the authentication token; and in response to authenticating access to the reward program account, execute the instruction.