once you up tier, very very difficult to come back down. i have not heard or read (maybe missed 0 of any successful case
Haven't really heard of any difficulty in doing so, but one thing about Simba's change of plan is that it happens immediately for
both upgrade and downgrade, and you lost whatever days left for the existing plan.
The existing plan must be in day 1-25 of the billing cycle, on day 26-30 you cannot change plan.
And if your plan expired, you cannot simply activate a new plan, you must top up to reactivate the existing plan (which is backdated to the previous expiry date) before you can change to a different plan.
That said, their Wifi Calling is more reliable than any other MVNO I have tried.
And I have been very satisfied with the roaming so far.
While the performance is not great, it has been pretty reliable for me.