A Hainault phone dealership has faced further complaints from customers demanding refunds.
Quick Mobile Fix sells refurbished mobile phones and carries out repairs at its warehouse in Roebuck Road.
It faced dozens of complaints over 2019 from people claiming their orders never arrived or were faulty.
In October the owner, Chinedu Emechebe, insisted that all those who were due a refund had been paid one.
His firm said the complaints occured in a tiny percentage of orders and added that QMF's employees had faced serious abuse and threats.
After two visits to the Hainault Business Park offices in 2019, Redbridge Trading Standards said it was monitoring the situation.
A spokeswoman said: "Our team will never hesitate to act against retailers who break the law or operate in an unfair way.
"There has been an increase in claims against this retailer from people who have experienced long delays in receiving goods.
"We have spoken to the retailer to inform them these excessive delays may be illegal, and further enforcement is being considered."
Legislation now gives QMF a grace period to reply and improve its compliance.
The company said the "vast majority" of refunds were done within the 14-day limit it guarantees online.
A customer, Sarah Marsh, 50, paid £133 for an iPhone SE on November 2. It arrived late and faulty on November 21, and she sent it back, asking for a refund.
She got her money back on January 12. QMF said in response it was going to repair the phone and could only refund her once checks were carried out.
"My story is a drop in the ocean," she said.
QMF said Mrs Marsh was refunded within 14 working days after checks had been carried out.
Ex-soldier and civil servant Colin Simpson, from Tynemouth, ordered two iPhone 7s for £396.98 on October 24. One was a birthday present for his wife.
"Several times I was informed the items were in quality control and about to be dispatched," he said.
"After waiting until November 19, my wife's birthday, and still with promises ringing in my ears, I cancelled my order and was promised a refund within 14 working days."
The refund did arrive but not until December 25. QMF said it took longer than usual "due to the busier than forecasted Christmas period" and this was "a rare, regrettable incident".
Mr Simpson, who has five daughters, was left £400 down before Christmas.
He said: "People have gone without presents and money at a time when you don't want to disappoint your family."
NHS worker Rachael Reeves was refunded £129.99 last Friday after ordering an iPhone 6 for her 11-year-old son - in July.
It was not dispatched on time. After asking for a refund and being told it would take 14 days, Ms Reeves requested a chargeback through her bank.
The device was returned on September 17 but QMF contested the chargeback, offering her a refund instead.
Ms Reeves said she sent more than 60 emails and lodged a claim in the small claims court before QMF sent her money back on January 16. The matter has now been resolved.
"I was bemused by the whole thing," she said. "I knew I was in the right; they had my phone and my money. It's exhausting and feels so unjust."
QMF said it was reasonable for it to contest the charge back before providing the refund.
The company said delays were caused by people requesting their money back from the bank, by its third-party refund software failing to process refunds on time, or due to its "thoroughly checking devices that are returned".
An ex-employee, Razaul Ali, claimed his team had a target of 55 email responses per day and on a Monday morning would have hundreds of emails.
A large number of these, he said, "were saying 'Where's my phone'?.
Embattled phone seller hits back at online "abuse"
Quick Mobile Fix said it had shipped out 40,000 orders in the last three months and said delays for technical reasons occurred in "a very small minority".
Responding through its lawyers, it said people raising charge-backs through their bank slowed down its refund process.
The firm said that incidents of threats and abuse, by email and on social media, had left its employees feeling "harassed and intimidated".
Membership of a public Facebook page for aggrieved customers has risen from 565 to 760 in three months.
Customers have also taken to Twitter and online reviews website Trustpilot to vent their frustrations.
On one occasion, QMF said, a client had to be escorted off its premises by police and employees had faced threats of violence and property damage.
Ex-customer Steve Tonge, from Manchester, who founded the Facebook page 18 months ago, said QMF was "leaving customers out of pocket for weeks".
"Some of the group's members are out of pocket by £500 or more," he said. "The financial and emotional distress this causes is heart-breaking."
He apologised for Facebook posts by customers in a "very emotive" situation that had caused offence, adding that he and other admins actively deleted abusive posts.
He said: "I would encourage QMF staff who are members of the group to report posts they feel are inappropriate."
The company has removed all contact details from its website.
QMF said its online chat function was available for five hours a day "on most days" and reducing its lines of communication meant it could "monitor, review and respond to complaints more efficiently".
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