Last year, Sandra Norman and her family spent nearly £5,000 booking a package deal for a villa in Rhodes for the end of May 2021, to celebrate family birthdays.
But Greece is still an amber-rated country under the government's traffic light system and the advice is to not travel to amber countries for leisure.
Sandra asked the travel agent if they could move the booking to the same dates in 2022.
She says the company refused to move the booking or issue a credit note, so if they didn't go on the holiday then they stood to lose everything.
BBC Radio 4's You and Yours programme has been contacted by people who booked holidays last year for summer 2021, or had holidays moved from 2020 by tour operators, who now feel they cannot travel due to government advice.
However, the travel companies are refusing refunds or delays to the holidays.
International travel restrictions for British holidaymakers were eased on Monday. 12 countries or territories have been given a green rating, meaning you can travel to them for tourism. But many tourist hotspots, such as France, Greece, Italy, Spain and Croatia, are amber countries.
The government's traffic light system is guidance rather than a legal requirement, and some travel companies have opted to still offer holidays to amber destinations if the Foreign, Commonwealth and Development Office has not advised against all but essential travel.
However, when you return from an amber country you have to self isolate at home for 10 days and take Covid-19 PCR tests on day two and day eight.
For Sandra and her family, it's not an option.
"My husband and son run a plumbing business, they have jobs booked in for the day we get back. I work, and we picked this time because the boys have an extra week off school. Now, when we come back they have to isolate, that's another week off school for the boys".
The company who Sandra booked through, Villa Plus, told You & Yours: "Government advice on amber destinations is not legislation and whilst we empathise with those that may now choose not to travel due to the entry requirements they face upon return to the UK, we cannot provide them with a refund or credit for monies paid and they should seek compensation from their travel insurance provider."
The company has agreed to make an exception in Sandra Norman's case, and has now offered to move the flights to the same dates next year and to issue a voucher for the value of the villa, which they can use to rebook once 2022 dates become available.
The UK's largest tour operator, Tui, is currently offering holidays to amber countries such as Cuba, Barbados and Antigua, and to some Greek and Spanish islands.
Lauren Bower and her family are due to fly to Gran Canaria on 4 June with Tui. They booked their holiday last summer, expecting things would be back to normal by now.
"I've got a five and a seven year old, we haven't got the option to quarantine when we get back, obviously with school and with my husband's work and my work."
The Bower family checked with their travel insurance provider and were told that their holiday insurance would be invalid if they travelled to an amber country against government guidance. Tui can offer the family travel insurance, but it will mean paying twice.
The company is offering customers free changes to holiday bookings if they don't want to travel, but they will be required to pay any price difference for the new dates, which can be more expensive because demand is high.
Lauren says her family would rather have a refund as their options to rebook are limited, having to use most of their annual leave from work to cover childcare in the school holidays.
"We can't do that because the one week we get off together as a family, my mother-in-law is getting married, so to go on holiday next year is not an option. And the price of holidays for next year have gone up already. If we were to go in the six-week holidays it would be an extra £2,200 on top of the price we've already paid."
In response to Lauren Bower's case, Tui said: "We're sorry to hear that the Bower family will not be able to take their holiday to Gran Canaria as planned.
"We're offering as much choice and flexibility as possible; all customers due to depart before the end of August can change their holiday to another time for free before the end of October 2022.
"Unfortunately in line with our Tui Holiday Promise, their booking does not qualify for a refund or voucher. This would only happen if we have to cancel their booking for operational reasons, there's a change in FCDO travel advice, or their destination is on the red list prior to travel."