so recently digi revised their smartplan lineup and im currently subscribed to the old smartplan 78
went to digi centre to ask whether existing user can change to new plan for free but they said existing user only entitled to plan upgrades
in my case smartplan78 to smartplan108/148 if i want to keep my number
either that or i have to subscribe a new line or MNP

my question is if i wish to retain my number whats the easiest or cheapest way to MNP to other telco and back to digi?
thanks in advance

for more info

went to another outlet again and they said it could be done without MNP they probably received wrong info