Fraudsters have become aggressive in recent days.
Spark has set up a scam helpline in response to fraudsters becoming increasingly aggressive this week.
The scammers are telling people their services will be cut off because of security issues if they don’t change their settings or clean up their computer.
Customers are then directed to a website where they are asked to download some software that has been branded by the scammers as Spark.
They are also being asked to give remote access to their computer, provide personal banking information and to leave their phone off the hook for three days following the “setting change”.
Some of the callers are giving a made-up employee number.
Spark’s manager of channel operations Richard Harrison said anyone with doubts about a call from Spark should hang up and ring Spark’s new scam helpline – 123 option 9.
“These fraudsters appear to be actively monitoring our activity and copying our methods of communication, so we know it can be difficult for customers to tell the different between genuine calls and fake ones,” Mr Harrison said.
“The most important thing to remember is that we will never ring customers out of the blue and ask them for any form of personal information – particularly bank details. We will only ask you for personal information if you call us.”
Mr Harrison said the fraudsters did not have access to Spark’s systems.