'No service" ??

Again having some troubles with simyo service :(:( In january i switched to simyo pre-paid from simyo abonament, keeping my number unchanged.
I had some problems then, got support from simyo and ...here we go again:/
This time i have problems with network. I have an ihpone 3 G. Since 2 days my telehpone can't connect to kpn network. There's "no service" message on the screen, i can't call and receive calls or sms's. I thought that maybe it's the iphone thing, so i reset it. No changes. I restored it completely - no better.
I slid into my iphone my friend's sim card (tmobile) - iphone was working perfectly fine, found tmobile network and so on.
So i dare to think simyo blocked my sim card, without a reason.
On saturday simyo took last abonement payment from my account and right after this my simcard stopped working ( no idea why, cause pre-paid and abonement are not connected ).
I would also add that my card is charged (still few euros on my account).
I'd appreciate your help to this matter. And if nothing helps, may i order another simcard?
If not i think i will switch to some other provider:(
with greetings,
Monika