Saudi operator Mobily requested a referral to arbitration after falling out with domestic rival Zain over what it claims is an unpaid bill.

The two signed an agreement back in May 2008 to cooperate across a range of services including national roaming, site sharing, transmission links and international  traffic.

Mobily claims it is owed SAR2.2 billion ($587 million) as of November 2013. Since then the operator has tried unsuccessfully to reach an amicable settlement with its rival. Hence the decision to revert back to arbitration.

Both companies have appointed their own arbitrators and are in the process of finding an independent umpire, said Mobily in a statement to the Saudi stock exchange.

The company has already had to provide SAR1.1 billion against total receivables due from Zain as of 30 October 2014.

The agreement between the two companies is, however, still valid, although Mobily said it generates only “irregular” payments from Zain for the service provided.