Freeview viewers complain that they have lost channels after planned changes were made to the network.
The company, which operates free digital television in the UK, warned users in advance that they may need to retune their systems today after the transmitters are updated.
However, many customers claim that their channels haven't been fully restored, despite retuning their TVs.
Freeview said anyone with problems should call their advice line.
Why are there interruptions?
The changes come after a government decision to reallocate some of the airwaves used by Freeview. In the future they will be used to develop new mobile broadband services.
The decision means that transmitters across the UK will be updated throughout 2020.
This week's changes are taking place in North West England, North East Wales and Creetown in Scotland, affecting around three million homes.
Viewers in these areas may need to re-tune the TV or box if they find that channels are missing. Paid satellite or cable services are not affected by the changes.
'I could do without this hassle'
Andy Seymour of Lymm in Warrington had trouble with his Freeview since 7am Wednesday morning.
After retuning, the number of channels he could watch dropped from 120 to 16.
"It's really frustrating because my daughter usually watches CBeebies on Freeview, while I need Internet bandwidth to work from home," he said. "I could do without this hassle as we address the current Covid situation."
Another viewer, who wishes to be anonymous, said they were reduced to six channels after a retune.
"I should be working today, not messing with my TV," he said. "What about all the old people stuck in because of the heat? Hopefully they have radio."
Similar complaints were made on social media by other viewers. Freeview told the BBC that it is working to help these cases.
"Retuning is a normal part of Freeview and most viewers find it easy," a Freeview spokesperson said.
"Information and advice on retuning Freeview equipment, including video guides for some of the most popular brands, is available on our website.
"Anyone who needs further help, or who discovers that channels are still missing after retuning, can contact the free advice line on 0808 100 0288, where our team will be happy to help."
