Telenor refused to say whether the offending staff member had been sacked or left his job voluntarily at the firm's Gjøvik facility in eastern Norway.
"We won't go into any details, but perhaps it was perhaps unavoidable with such a serious incident," Telenor spokesman Tor Odland told newspaper VG.
The unsavoury incident happened last Thursday after 16-year-old Maiken Fredriksen Iversen phoned Telenor to make a complaint. Minutes later, a disgruntled customer service agent sent her a text message to say he hoped she would burn in hell.
The 16-year-old from Kirkenes contacted the Norwegian operator on Thursday to ask why she had not received a warning message when she was about to exceed the monthly limit on her subscription, VG reported.
“He told me to download an app to keep a check on my usage,” Iversen told the newspaper.
“I said that shouldn’t be necessary, since I’m supposed to receive a notification via SMS. He then asked me to ‘be a little bit helpful’. I said that wasn’t good enough but wished him a good day before hanging up.”
A few minutes after the call, Iversen could hardly believe her eyes when a text message arrived from a Telenor number:
“It’s rare to encounter this level of cheek. Hope you burn in hell!”
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Another message from Telenor informed Iversen the company had activated a mobile broadband service which she had not requested.
Furious, the girl’s mother, Mette Fredriksen, called Telenor to ask for clarification. When the company failed to get back to her with an apology, Fredriksen reported the matter to the police and went to the media.