Hi Josh
The problem with setting another DNS server in your computer network settings or on your router is that Telkom is doing some kind of DNS grabbing/hijacking and there is no easy solution to bypass this.
That's now my conclusion too. Just spent more time resetting winsock, ipconfig /release/renew, netsh int ip4/6, flush dns, etc. Multiple computer reboots (boring), even though my PC is quite fast with lots of RAM and a 500GB SSD.
As for VPNs - I've used several over the years (both free and paid-for). In moments of cerebral weakness, (or just nearly drunk), Betternet (free version) works "OK", but no servers to choose from.
My paid-for VPN is IPVanish which seems pretty good for me. Of course, there are oodles of other ones vying for our money. Tracking down the best deals, best "anonymity", best trial version, best ease of removing, customer service, most world-wide available servers, least impact on download/upload speeds, prettiest (and most user-friendly) interface, easiest installation process, etc, can take lots of time.
I signed up, paid and trialed several well-known ones, which didn't/wouldn't work properly for me. Then spent days/weeks with "customer support" to resolve "issues", eventually cancelling and then tried to get my money back.
(Not always as easy as they promise - some are better than others.)
I'll
try and tinker with my Telkom Alcatel modem settings, but as you say, some changes might "work" at first, until they don't.
Another ISP might be better for me, (and even cheaper), but the one I've got my eye on is not available yet where I live.
Or - there's a Telkom wifi outdoor depot at the end of my street which is offering speeds of "up to 100 Mbps", for Rp 50,000 a day (24 hours).
I tried it once so far and got 15+ Mbps download speed, (still faster than my 10 Mbps IndiHome package).
Unfortunately, it's too hot sitting there in the heat, no immediate refreshments available, and virtually no "privacy" (as if).
Could go in the middle of the night, I suppose - they provide power-point outlets so we can plug in our laptops, charge up our smartphone batteries, etc.
I might try it some night - hopefully, it won't be raining.