(I wouldn’t personally use Belarusian SIM cards I don’t want to be sent to a gulag! but none of MTC, Velcom, life nor beCloud are on that list, FreePBX firewall access should likely be before ipset blacklist in your iptables chain perhaps ?)
Belarusion ASN on the list are
6697 | 37.215.244.186 | 37.212.0.0/14 | BY | ripencc | 2012-03-30 | BELPAK-AS BELPAK, BY
6697 | 37.215.83.127 | 37.212.0.0/14 | BY | ripencc | 2012-03-30 | BELPAK-AS BELPAK, BY
6697 | 82.209.235.209 | 82.209.192.0/18 | BY | ripencc | 2003-10-01 | BELPAK-AS BELPAK, BY
50590 | 93.125.1.208 | 93.125.1.0/24 | BY | ripencc | 2008-04-15 | NETBERRY-AS, BY
25106 | 134.17.94.57 | 134.17.88.0/21 | BY | ripencc | 2011-11-03 | MTSBY-AS, BY
6697 | 178.124.209.209 | 178.124.208.0/22 | BY | ripencc | 2009-12-10 | BELPAK-AS BELPAK, BY
6697 | 178.124.214.18 | 178.120.0.0/13 | BY | ripencc | 2009-12-10 | BELPAK-AS BELPAK, BY