You have a internet connection with your ISP - congratulation.
But your MikroTik RouterBoard LHGR should have got access to internet itself, befor we can say about sharing this internet.
Then you should do a some testings:
check if pings give you access to some remote host
ping 1.1.1.1
check if you can see path of internet IX way to your final target
tool traceroute 1.1.1.1 use-dns=no
check if your ISP not block you a DNS service
put [resolve myip.opendns.org server=208.67.222.222]
Check what DNS service ISP give you (check the dynamic-servers and servers field):
ip dns print
Try open some webpage from telnet at 80 port like (if you have Connected then type "get" command with enter):
system telnet port=80 google.com
Try read a SMS from ISP who can send you SMS like "You have limited connection, wrong plan, without $ at account, we not like your IMEI device and change to phone bcs you have phone plan, etc..."
/tool sms set receive-enabled=yes port=lte1
/tool sms inbox print
Yet, still all this can not work even you are connected.
Why? Because some ISP must have proper ISP, proper Plan, proper device, proper location (bts) and other ISP restriction.
I hope that stuff give you some help.
Give us feedback !