Avoid answering the phone number 0141 839 5344 it is used by scammers who will attempt to extract personal details and even you bank details. Callers pretend to be phoning from the HMRC. One tactic they use is to suggest you are under investigation by HMRC for fraud. They will then bully victims into passing on their details.
Do not be a victim of this scam, instead hang up the phone and report it to phishing@hmrc.gov.uk