erm, nope i don't think so.  so far as i know, once you subscribe to umi28 you're basically stuck with it for a month,  and all you can do is cancel the auto-renewal so you can subscribe the new plan upon expiry the one month.  at least, that was my experience with U Mobile's broadband options.  got any sifu here know differently??

You can resubscribe though within the month of the subscription itself, but you will lose your free sms, call etc if you're not subscribing to the same plan(UMI28 must resubscribe UMI28, if you subscribe to UMI48 then you will lose your free calls and sms).

There are no rollover of data quota I believe as there's this one month that I didn't used up all my data, but the next month the apps reported that it has reached 500mb then my speed become........   
http://u.com.my/prepaid/umi_tnc

erm...... one response by me:  

when do you see postpaid users go and buy reload cards? 

well, for the no termination, registration fee and contract, that's true though.

For the speed, another  . I'm using the umi28 prepaid and I can easily get 1-2mbps at my home(the H only got two bar only  ) and 3-6mbps(4 - 5 bar of signal) at my college

If you've used up all your quota, then your speed will be throttled to 64kbps(can whatsapp but surfing?  ). No additional charges. If you auto-debit, you can get 250mb extra.

no, I mean she said that the highest speed for prepaid is "126" kbps(I can get at least 1mbps at my area) so .......   

Postpaid UMI28:
- 1gb quota
- 100 free sms

Prepaid UMI28:
- 500mb quota
- 100 minute call
- 30 sms

But if you pay via autodebit then can get another additional 250mb.