CalypsoBTS + GPRS and SDR suggestion

Hi everybody, I'm pretty new to the GSM/UMTS environment and I'm doing some tests. Currently I need to analyze some IoT devices that use 2G network to comunicate via GPRS. I setup CalypsoBTS to work with 2 old motorola c123, I know that isn't the best way to do that, but I would like to have a cheap solution. I got the setup working with a normal phone and the BTS seems to work correctly (using jolly/testing), but from my understanding it support only GSM calls and SMS and GPRS is not implemented into the transceiver. I'm wrong or this part has not been implemented yet? If needed to use a GPRS BTS can you suggest the best cheap SDR to use with OsmoBTS? (I saw BladeRF and LimeSDR but I was unable to understand if they are full supported via OsmoBTS) Thank you in advance. inode