Japan’s smallest cellco, Softbank Mobile, has been forced to suspend Mobile Number Portability applications twice over the weekend as the operator struggles to cope with demand.

To some degree, Softbank, which last week launched a price assault on the market just as portability was introduced, has become a victim of its own success. But some reports also suggest that the high number of requests from users wanting to leave the operator is contributing to the struggle.

Mobile Number Portability (MNP) allows subscribers to take their phone number with them when they move to a different carrier.

Last week, Softbank made much noise about undercutting the tariffs of its rivals by Y200 (£0.89) and pledged to respond to reactionary cuts made by market leaders NTT DoCoMo and KDDI within 24 hours. “If they drop prices Y1000, so will we,” Masayoshi Son, president and CEO of Softbank Mobile, said at a conference.

It is understood that Softbank’s computer system has insufficient capacity to handle the requests. According to the Financial Times, both new applications and cancellations were much higher than the company had expected, although it is not clear if the operator is winning or losing more customers.

Both incoming and outgoing applications are understood to have been suspended between Saturday afternoon and Sunday afternoon and again on Sunday evening to have been resumed earlier today.