To recieve Pager messages (POCSAG) you need multimon-ng.
multimon-ng a fork of multimon. It decodes the following digital transmission modes:
POCSAG512 POCSAG1200 POCSAG2400 FLEX EAS UFSK1200 CLIPFSK AFSK1200 AFSK2400 AFSK2400_2 AFSK2400_3 HAPN4800 FSK9600 DTMF ZVEI1 ZVEI2 ZVEI3 DZVEI PZVEI EEA EIA CCIR MORSE CW
If you already installed multimon-ng in step 5 skip the installation below
git clone https://github.com/EliasOenal/multimon-ng.git cd multimon-ng mkdir build cd build qmake ../multimon-ng.pro make sudo make install
And just run
rtl_fm -f 172.45M -M fm -s 22050 -l 250 | multimon-ng -a POCSAG512 -a POCSAG1200 -a POCSAG2400 -a SCOPE -t raw /dev/stdin