(Reuters) – Italy’s competition authority on Thursday said it had told the country’s biggest bank Intesa Sanpaolo (OTC:ISNPY) to halt the proposed transfer of 2.4 million customers to its new mobile-only service Isybank.

The decision is the latest blow to Intesa’s efforts to update its digital infrastructure and gradually abandon legacy systems in favour of cloud technology.

“In this way account holders will be put in the condition of choosing whether to keep their account with Intesa Sanpaolo … or shift to Isybank,” antitrust agency AGCM said in a statement.

It was not immediately possible to reach Intesa for comment.

The authority opened a probe earlier this month into the way Intesa was transferring clients to Isybank after a raft of complaints which the watchdog said had now reached 5,000.

Isybank targets 4 million Intesa customers under 65 who only access their banking services remotely. It wants to add also 1 million new customers by the end of 2025.

The group migrated the first 300,000 Intesa account holders in October and plans to shift another 2,4 million in early 2024.

Isybank, a cloud-based, low-cost mobile bank, is a key plank of Intesa CEO Carlo Messina’s long-term strategy to withstand competition from fintech and focus Intesa on more profitable businesses such as wealth management and insurance.

Shifting bank services onto a cloud platform is a major challenge for mainstream banks, whose IT infrastructure is outdated and often made unwieldy by the overlapping of different systems resulting from bank mergers.