I received a call stating that i have an unclaimed postmail from my local singpost branch. the phone number asked me to press 2 review the package and suddenly the caller hung up on me. Note that SingPost doesn't have such a process. If an item is undelivered, they will NOT call you but instead will leave a note for you to collect your parcel from a SingPost branch or Popstation. 

https://www.singpost.com/online-security-you

If in doubt, call the company's official hotline to check.