Smartphone. Truemove

I was gifted recently a Samsung Galaxy 3 Android phone, and I promptly inserted my TrueMove International Prepaid SIM. No mobile internet except via my own Wifi at home, not ideal, I can just use my laptop at home!

So I was advised (by the manager of a 7/11 no less, after I badgered them about "GPRS gredit" that my phone mention) to *9000 to apply a Wifi / EDGE / GPRS package. I did, it took 24 hours but eventually it came through - and immediately tanked out my remaining 150 baht or so credit. I topped up again, this time by 500 baht and I woke this morning to find that too all gone, with several messages from True to the tune of "Your remaining credit is 35 baht, 62 satang. You can refill at any 7/11 blah blah" and "Your True Move credit has been withdrawn for 12 baht 84 satang".

Obvious I am somehow using vast amounts of data... well, er, I'm not, this all happened at home on the wifi. dam_n. Anyway, I need to move to some sort of unlimited usage 3G package - perhaps whatever plan they give you with an iPhone. Can I do this prepaid?

Or can I switch to another network and keep my old number, as you can in other parts of the world? Ive recently sent out dozens of CVs with this number on it.