i upgrade from Streamyx 8M to unifi (via a agent), i didn't need to pay RM100, this is my first bill, seem like i got a month Waiver ( Promotion?? )

previous month,
how much did you paid?
When did you make the payment ? did you make the payment during/after on 4/4 ?
in the bill statement, did they include proof of your payment?

"For March I paid RM69+RM10[RC fees]+6%SST=RM83.75"

I think it's possible that the bill you paid was for a previous unifi lite account because there was a reconnection charge. while you just upgrade to unifi fiber in March.   

Overpayments for old accounts are not carried over to new accounts. otherwise it will be returned in the form of a check.

Yes, you need to make a new payment on the new Unifi account number

Maybe you can show your bill charges so that someone who know can help. Just blank out the account number and address. For UniFi/Streamyx, the first bill will be paying for 2 months. So you pay in advance.

did you make payment for unifi lite account before or after upgrading to fiber? If you make a payment before upgrading to Fiber it is not a problem because the unifi lite account is still active, if you make a payment for a unifi lite account after upgrading to fiber it will be a bit of a problem because the unifi lite account will be terminated automatically after the unifi fiber installation is completed on your premises at the same time. Although it is displayed "still active"

23/3/2021 - you have made a payment of RM 73.15 on the old account, and there is an overpayment. The overpayment will be refunded via check. And your old unifi account was officially terminated on 21/3/2021 which is 2 weeks after the unifi fiber installation. It was a little late for that period.

On my old unifi account, it only took only 5 days to close the old account after installing Unifi fiber. After my old account is terminated, my home phone number that has been entered into the modem can be used because the process has been completed within the 5 days. (The period given to terminate the old account is up to 14-21 days.)

From what i see, u have 2 account. 1 for your old unifi lite account and another 1 is your fiber account. Your old account will automatically terminate once your fiber account is activated and the extra money will return to your by cheque.

For your new account, you need to start fresh.

by itself

I was told by the installation, he said the process of migrating from an existing phone number to Unifi fiber takes up to 14 days, so I expect the process of terminating the old account takes 14 days. Only after my old account is terminated within 3 days, then my existing phone number can be used on the unifi modem