I did not get charged RM200 for the "downgrade" but got locked into another 24 month contract.
Bloody hell it should be called an upgrade, not a downgrade.
Anyway, my own experience of getting the RM 129 100Mbps package ("downgrade" from Rm 139, 30 Mbps Bonanza package) is rather similar to a few others on the forum:-
1. Went to Damansara Utama (Uptown) TM Point at 9:00 am to find a queue already forming inside. Consensus seems to be that many are switching over to the new package.
2. Was 5th in line. Had to wait for 30 mins before I was tended to. Mentioned that I wanted to change my package to the 100 Mbps one. Staff at the counter mentioned a combo for RM 159, I just persisted on the RM129 package. He relented, and mentioned that I wouldn't qualify for the free turbo. I told him that since I had just moved to Unifi 2 months ago (July 2018), I wouldn't see any Turbo until next year at the earliest and 3x Download Speed/5x Upload Speed for RM 10 cheaper per month was too much for me to pass up on.
3. He informed me that a technician will have to visit the premises later next week (tentatively Monday) and after which the upgrade would be applied. I was puzzled since my TM provided equipment (ONU/Router) is brand new and only 2 months old and should definitely support 100 Mbps. I also thought that they could adjust and apply the new port speed on their end without visiting my premises.
4. 3 hours later the account was adjusted to the new 100 Mbps (STB) plan and the PPPOE connection reset itself, reconnecting at the upgraded speed.

I'm pleased with how seamless and fast it went. Big thumbs up to TMNUTZ.
. I will visit my nearest TM point next week.