in the FAQ, i only found prepaid upgrade to black plan but not the other way round.
http://xox.com.my/support/terms-and-condit...nexox-black-tc/

anyway, since black is contract free, you should be able to do that. call the support to confirm.

just port in yourself, why need dealer? apply through website and get the SIM card first.
https://xox.com.my/onlinestore/mnp/portinginfo_black.php

as long as your outstanding bill is ZERO, you'd have no issue to port over. i ported over from celcom 1 week before billing date with zero outstanding bill, no charge for the following month. login to celcom website and it's nothing there since my number have been port over to onexox. no email billing in the following mth from celcom also.

guys, been using B39 for a while now. if i downgrade to B10, will my current data/talktime/sms remains? couldn't find this in FAQ

they have removed it from the website, maybe new plans coming soon?
anyway, these are the old ones currently available for upgrade.

it all depends on your usage... for me, black is worth my usage than prepaid.

it didn't said not eligible for onexox black, as long as new subscribers should be eligible.

Who is eligible to purchase?
Season Pass Welcome Deals are only available to all NEW SUBSCRIBERS (via MNP or new
activation pack), including new subscribers who had activated their SIM Pack from
1/9/2018.

How many packages does Season Pass Welcome Deals have?
There are FOUR (4) Season Pass Welcome Deal packages available:
a) SP FAT 10GB+10GB = SP FAT10
b) SP FAT 10GB+333mins = SP FAT10M
c) SP FAT 5GB+100mins = SP FAT5M
d) SP FAT 333mins = SP FATVOICE

https://xox.com.my/wp-content/uploads/2019/...FICIAL-Sean.pdf

i saw the seller replied to you on the difference. btw, official onexox don't have B59DB plan.

i was on B39 with my data accumulated 96 GB (max carry fwd is 100 GB) so downgraded to B10 in Aug, everything is intact - now at 97 GB. I also confirmed with the ONEXOX staff at their branch.