Is Microsoft Access being phased?

I think theDBGuy is probably correct. That falls under the category of people misinterpreting what they see or read.

It was from someone who works with a commonwealth government agency, as they have been told that's what's happening and they are building something else to use.

It's highly likely that they were simply referring to themselves rather than Microsoft. For example, in one place of work that I know of, they are starting to phase out Microsoft Access from their ecosystem because of tightening security requirements. No macros of any kind can be executed unless it's digitally signed with a verified digital certificate. And because the company didn't want to invest in a digital certificate framework, people are starting to find another way of doing their jobs without using Access.

It was from someone who works with a commonwealth government agency, as they have been told that's what's happening and they are building something else to use.

So ask them where they heard it!

The reality is that Access has always been denigrated by IT departments. This is generally due to IT departments wanting control over their data but Access shifts some of that control to end users. There is some sense in their feelings, but there are workarounds.

But there is no truth to this rumor, and its likely this person is being fed a line.

I have heard that Microsoft Access will be phased out in 2025 and it will no longer be available at the end of this year. Is this true?

I think the best indicator that statement is not true is that Microsoft has very recently setup the Standalone Access: Buy Microsoft Access – Standalone Price & Licence | Microsoft Store

It appears that Microsoft will not be selling Microsoft Professional 2024. This is because Publisher has been retied. Professional version would not be cost effective. Buy Office Home & Business 2024 for PC or Mac – Download & Pricing | Microsoft Store

£250+£160=£400 Office Professional cost £440.

PS: Compare Microsoft Office Volume Licensing Suites | Office LTSC is designed for small businesses. (The Pro Plus version having Access PC Only)

As the others have already stated there is no truth to that statement.

Ask them to provide a Microsoft document/webpage with such information. They won't be able to.

I can also state that Access is under active development by Microsoft, refer to the official Roadmap to see what is currently being worked on by the Development Team: https://www.microsoft.com/en-us/microsoft-365/roadmap?filters=%5B%22Access%22%5D 

It is possible that they are referring to the EOL (end of life) for a specific version. Say Access 2019 EOL whose extended support is Oct 14th, 2025, but that is inconsequential as it will continue to run just fine for years or even decades afterwards and newer versions are always available (Access 2021, Access 2024, Access 365) if wanted.

People may also jump to the conclusion that Access is dead since there's not a single consumer version of Office with Access anymore! But, you can still buy it as a standalone application or via a volume license purchase (if you have access to that) or part of most MS365 subscription plans.

All of this to say Access is still active and isn't being retired in 2025.