NS&I has issued advice to a man trying to merge two accounts that were set up 50 years apart.

The customer contacted the Premium Bonds provider over X to ask: "I have two accounts with you.

"One I started in 2006 (I think) and another was started for me in 1956. Is it easy for me to amalgamate? I am not in the UK."

A representative of the savings giant said in response: "To merge your account, please write to us at NS&I, Sunderland SR43 2SB with a signed letter.

"Please include your name, date of birth, address, your current NS&I number you log in with, and details of the missing Bonds.

"If the name and/or address is different on the old Bonds, please include your previous details as well."

NS&I also sent him a link to this webpage with more information about what information to include when writing to the provider.

The man also said he was having a problem logging in. He asked: "I am trying to log into my account but am unable to.

"I have my holders number and the password I set up several years ago. And I know my name. But says incorrect?"

The representative said: "To log in, you will need your NS&I number which is different to your holder's number. You can try to retrieve your NS&I number on the login page by clicking on 'Forgotten your NS&I number'."

Another customer recently got in touch as some funds had been returned but they were unsure who they belonged to.

He said: "My parents have tried to open two accounts for our children. At this point, several weeks in, one amount of investment has been returned, we have no idea which child this relates to, or why.

"We're also not sure whether the other application has been accepted. Chaos."

The man added that he was trying to fix the issue over the helpline but had not got anywhere.

He fumed: "I'm currently on the phone to your team, armed only with letter references, and it seems they can't be sure what is going on either.

"Their best suggestion has been to reapply - but for which child? And why should I believe this won't happen again?"

A representative of NS&I responded to say: "This can be cleared up for you by calling our secure phone line on 08085 007 007.

"One of our advisors will be able to assist you with this, one of the responsible parents named on the application will need to call for this to be looked into."

For the latest personal finance news, follow us on Twitter at @ExpressMoney_.