The net of the Tunisian Telecom is stabile and in very good condition. Cell phones work from the northern most coast of Tunisia down to Douz, several foreign nets are able to roam in the net. The mobile net of the Tunisian Telecom has the net number "60502", at the coast, there is sometimes the roaming in italian nets possible.
At our last tour in  Januar 2001 , the GMS net covered Tunisia from the coast down to the line NEFTA-TOZEUR-DOUZ-GHABES-DJERBA . But gaps can always occur.
The oasis KSAR GHILLANE however doesn't have a GSM net and is not reachable with a phone .

The phoning in hotels is very expensive. So you should phone in one of the many Taxiphones.

Ein Taxiphone

The prizes for a overland call per minute in Tunisia over the net of the Tunisian Telecom are about 20 Pf or about 10 cents ,  for a call to west europe,  about 80 cents per minute.