Question: can I connect through a VPN with Telkom LTE?
Yes, I've just double-checked on an Android phone using the "VPN Free" app., through Germany.
Can provide screenshots if you like, but I can't prove it was Telkom as it was via wi-fi so the SIM's in the router.
In the relatively recent past (maybe 4 - 6 months ago ?), I used Proton VPN on a Linux-based laptop with the Telkom 100 GB night data bundle without issue/s.
EDIT : if using the free VPNs, you sometimes won't get the country you choose, so check up on https://www.whatismyip.com/ after connecting to a VPN, to see which country you're really based in.