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Mobile phone users are unlikely to get a respite from the menace of pesky commercial calls and text messages anytime soon as the majority of these come from unregistered telemarketers (UTMs) using personal mobile numbers that are almost impossible to monitor or bar, say senior telco executives.

Spam calls — or "scam calls" as they're also known — have become an infuriating part of life. By now, most people are well acquainted with fraudsters trying to dupe you out of your cash by impersonating government officials or Amazon employees.