Do you go through the correct process? To switch from Unifi to Maxis, first you go and register your Maxis Fibre. Bring along your Unifi bill so it's easier for them to trace your address.
After register, bring the transfer ID, go to TMPoint and inform them you want to switch ISP. TM will process the switching in 10 working days and release the line to Maxis. It's just like MNP.
Gone are the days you can install Maxis first then terminate Unifi.

If you cannot walk in to both TM and Maxis center, maybe there's some agent which can help you settle everything.

Usually if register at center the TR code is instant. Anyway keep us updated.

so how's  the performance after switch to Maxis?

In terms of stability, definitely UniFi is much better, been using my Maxis Fibre for around 1 year, facing a lot of issue which including packet loss, ping spike and slow speed during peak hour. The technical team came to my place replaced a new router for me but the problem still persist. I believe the bandwidth of Maxis Fibre around my area is congested, therefore the issue arise only during peak hour. Luckily Maxis Support is surprisingly quite good for my case and their customer service is available 24 hours, currently trying to make a follow up complain to Maxis, hopefully they will fix my issue. Beside this, Maxis One Prime is pretty much worth the money thou, this is the reason I'm still staying with them.

Finally, last contract month on UniFi. Going to switch to Maxis. So I need to go Maxis Center to apply and submit transfer ID to TM. Right?

For those who just switched, any downtime when porting from UniFi to Maxis?