Vee Raine, from Llanelli, said she had paid in £175 since August to spread the cost of gifts for their four children.
Ms Raine said she had been unable to contact MWC World since reaching the target amount on 1 November.
Owner Kelly Jenkins said she had been dealing with a family bereavement and her father had had a heart attack.
Ms Raine said she knew of at least six other families who have been affected and are still waiting to receive the items they ordered, or a refund.
Ms Jenkins added she was sorry to have caused concern and that “everything will be sorted before Christmas”.
Ms Raine and husband Chris have four children – 14-year-old Cori, Kayden, eight, Bella, six, and six-month-old Amara.
In an effort to make Christmas spending more manageable, Ms Raine sought the services of MWC World, a sole trader business based in Llanelli, Carmarthenshire, offering a voucher saving scheme for toys, clothes and electrical goods.
After making weekly payments since August, the time came in November to receive the items she had paid for.
Ms Raine said she received an initial reply from Ms Jenkins to confirm it was “all fine”, but the conversation suddenly stopped when arranging delivery.
The MWC World website has since displayed a “we’re down” message, although the company’s Facebook page is still live.
“I was a bit nervous,” said Ms Raine, who is concerned it will ruin Christmas for her younger children if they don’t receive their items.
She said: “My eldest is 14 and he gets it, but the two middle ones are the most concerning because it’s all very magical for them.'”
In an unrelated incident just weeks before, Ms Raine said the family were the victim of a theft in which £100 of Christmas savings were taken.
“We are pretty resilient – the children won’t go without, but it’s hard,” she added.
Ms Jenkins apologised but claimed it had been “blown out of all proportion”, and called on people to “work with us” by not being “rude”.
She said some people had been to her house to claim their items or money, which had scared her children.
‘I’m a mother myself’
“Of course people are going to get their stuff, I’m not going to leave them without anything – I’m a mother myself,” said Ms Jenkins.
Concerned customers can either claim the money back through their bank or PayPal, or wait to receive the good they ordered, she said.
Ms Jenkins added she had been operating MWC since 2017 “and had never had an issue”.
Dyfed-Powys Police said it was investigating “a number of reports… that people have paid money into a scheme but have not received the items they have ordered”.