Jenny Stephen expected BT to connect her home to a telegraph pole visible from her window at a holiday village in Corton, Suffolk.
But BT Openreach quoted her a price of £18,799 plus VAT, saying it was due to the "huge" civil engineering task of laying 400m of underground cables.
Mrs Stephen said: "Maybe it's because I'm old, they think I'm stupid."
She retired to Waterside park on the coast 18 months ago and since then has tried to get BT to install a phone line.
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A neighbouring property has been linked by an overhead line to the telegraph pole on The Street, which is adjacent to the holiday park.
But BT told Mrs Stephen it would have to dig up the road to install her landline.
"[I'm told] there's no option, although a radio link or a link to another house would work," added Mrs Stephen.
"I just want to make a phone call but I can't get any sense out of anybody."
BT said: "The price quoted is due the huge civil engineering task to provide an underground service to one customer in Waterside Holiday Park.
"In this instance nearly 400m of cabling is required, as well as the need for surveys and complex underground duct work to be installed."
The owners of Waterside said it would be happy for BT to run overhead cables to Mrs Stephen's maisonette.
A woman who asked BT to install a landline at her home was told it would cost more than £22,500.