Customers arrived at stores in the Mall of the Emirates before they opened, with lines snaking through the centre as the day went on.
“Since we opened we have already registered more than 500 people,” said Vishwanath Krishna, supervisor at the du centre in the mall.
“There were queues of people even before we opened and we expect it to get busier as the day goes on and also in the next days before the deadline.”
Re-registering was ordered as part of the Telecommunications Regulatory Authority’s My Number, My Identity campaign, launched last summer. The deadline only applies to people who have received a text from du or Etisalat.
But there was confusion, with people who had not been contacted among those queueing for more than an hour to register.
“We heard about the deadline and so I came here with my daughter to get her Sim card registered,” said Maha Zakaria, a German national who was at the du outlet.
“I had no idea that the deadline was only for certain people. It’s a very confusing situation as I also have to register my husband’s phone.”
For others the inconvenience of having to register during office hours made it difficult.
“We will be here for at least an hour and a half,” said Asif Javed, a Pakistani.
The line at the Etisalat outlet outside the Virgin Megastore grew to about 100 before midday.
“I came here to register because some work colleagues had mentioned it and I was worried that my phone would get cut off,” said Mohammed Hassan, an Egyptian, who had not received a text.
“I might as well wait in line and get it done now but it seems to have been a waste of time.”
Louise Kidd, from the UK, received a text this week asking her to re-register. “I’m not sure how long this is going to take as the line is long and I have to do the school run. I might have to come back on Wednesday,” Ms Kidd said.
She added that the campaign should have used more than one method to contact customers because many people did not realise the significance of the message.
“We have had to turn a lot of people away who were trying to register other people,” said Mohammed Abu Sumama Khan, a sales executive with Etisalat.
“The person who the Sim card belongs to must register in person.”
Registration requires customers to fill in an application form and take a valid passport, residency visa or Emirates or GCC identity card.
The campaign aims to ensure that the owners of Sim cards are the ones using them, to tackle fraud.