A phone company has launched an investigation after a "substantial" number of people in Exeter received repeated silent late-night phone calls.
Some householders said they were "very distressed" after getting as many as seven calls in 12 hours, leading to a disturbed night's sleep.
British Telecom said it had received a number of complaints and had alerted Verizon, the company responsible.
Verizon said the calls had now stopped and it was "looking into the matter".
Your first thought is maybe it's one of your family, that there's something up with them
Sylvia Downing
Pensioner Sylvia Downing said that on Monday night she had seven silent phone calls in just over 12 hours.
"Your first thought is maybe it's one of your family, that there's something up with one or other of them.
"That's what annoys you more than when you go down there and there's no-one there," she said.
Sylvia's daughter and granddaughter also had the same phone problem, as did Brian Snell.
He said he was woken for the first time at 0200 BST
"I picked up the phone, nothing. I'm very annoyed about having to do that.
"I went back to sleep eventually and then six o'clock, lo-and-behold it goes again.
Nuisance calls
Another resident, who asked not to be named, said the calls made her "physically sick".
"It got to the point at 3.45am, after five calls, I was so tired that I had to run to the bathroom after I put the phone down."
She said she wanted to know how Verizon had got hold of her number and has made an official complaint to phone regulator Ofcom.
BT said it had had a substantial number of complaints which have been passed on to its nuisance calls department.
Verizon, based in Reading, said: "Verizon Business has been informed of various incidents concerning silent calls in the Exeter area, purportedly originating from a Verizon Business customer.
"The company is looking into the matter and will respond further as soon as more information is available."
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