Customers of the luxury grocer Fortnum & Mason have been complaining about difficulties placing orders and getting a response from customer services during a busy Christmas period for the retailer.

Some shoppers at the store, which holds a royal warrant and is famed for its Christmas hampers, have taken to social media and review websites to complain about being charged multiple times after repeating transactions thinking they had not gone through.

Many have also complained about the retailer’s customer services team and how long it has been taking to get help.

One shopper included a screenshot of her phone with a call time running to one hour and 27 minutes. She said: “This is the hold time.”

Another got in touch with the Guardian to say she had been charged multiple times for the same item, describing the incident as a “fiasco”.

Fortnum & Mason denied that there were any issues with its website, saying it was “very busy” and that Christmas demand had “arrived late this year”. It said it had the same customer service setup as it did every year, bringing in extra support for the festive period.

The customer who contacted the Guardian, asking not to be named, tried to order an e-gift card, and then “pressed pay” using a credit card but said, “nothing happened” and she did not receive a confirmation email.

“When it didn’t work with the credit card, I tried with my bank debit card,” the customer said. “The same thing happened. There was no confirmation, and when I clicked pay, there was no [confirmation] email. I checked my bank account and £50 had gone out.”

When she called customer services, she said she was waiting on the phone line for an hour. The customer was able to stop the payments, but if she had not, she would have paid £200 to Fortnum’s “and received nothing in return”.

The retailer, founded in 1707 by William Fortnum, a royal footman, and his landlord, Hugh Mason, is popular for its Christmas hampers.

On the review platform Trustpilot, some customers have been expressing their frustration. One poster said the “chat support facility does not connect to an operator”. They said they were on hold for an hour before they got a response.

Another reviewer reported having to amend an order and that Fortnum & Mason was “absolutely uncontactable”. The reviewer tried six different ways to get in touch, including email, Apple chat and phone.

A further reviewer spoke of ordering three family hampers, retailing at £260 each, and receiving no confirmation email. “[I] logged into my account to find no record of my order, but did screenshot the order confirmation, so had my order number.”

The reviewer then checked their bank and found the money had been taken out. They claimed customer services said there had been a “glitch” and “would get the order manually put on to the system”.

A spokesperson for Fortnum & Mason said: “We’re not experiencing any issues with our site, but we are very busy, and Christmas demand has definitely arrived late this year. That said, we are delivering customer orders on time and in full.

“We have the same setup as always on customer service in terms of answering calls – we always bring in extra support for this very busy period. We’re definitely seeing a lot of late demand this year, so we’re encouraging customers to use our live chat and other channels rather than email so that we can service their queries as quickly as possible.”