Probably a telemarketer as I called back a few times while masking my number with 1831 prefix and after a prolonged silence it gave an engaged signal - a usual sign something isn't right. Blacklisted!

Scam/spam caller as one of 5 consecutive days of unknown callers numbers 3 from ‘UK’ , 3 mobiles and 2 landline numbers … always after my contact with my telco, or utilities or insurance company!