Hi
My name is Herve and I work at telna Mobile. We just launched a new international roaming service that looks like all the ones you are mentioning in this post. It took us many years to work on it as we didn't want a service that would go down as quickly as many others you mentioned in this thread.
The reason I post in this thread is that we decided to waive our first year of annual fees for former celtrek customers as long as they still have the celtrek SIM card. The reason is that we would be able to switch those cards onto our network and make them work with our equipments. Our company would save, so we share the savings.
Our service is not prepaid, it is postpaid. But at this time we only sell it to customers in the US (sorry for the others).
You can check our website at
telna Mobile - Low cost cellular service for international travelers(reduced roaming for inbound and outbound calls while abroad)
I'll keep an eye on the forum for your questions.
Thanks for looking!