Below reply from TM support email.
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response on the said matter.

Kindly be informed that new packages price is depends on the current promotion. However for existing unifi customer that apply to downgrade the unifi package to
any of the Campaign Packages, a new twenty-four (24) months minimum subscription period will be imposed on the new subscription. Thus, should you wish to downgrade to the packages, you are advised to refer any nearest TMPoint regarding this promotion.

For the nearest TMPoint, kindly visit our website at:
https://www.tm.com.my/OnlineHelp/TMPoint/Pages/Home.aspx

i chat with CS, they mentioned STB will be maintain! price also RM 129 also no extra charges...