A deposit transaction and a membership upgrade transaction are two different things.
An account’s membership should be upgraded immediately if the account balance is sufficient to cover the membership change. Otherwise, you will be asked to deposit funds to the account, which will be just a straightforward deposit transaction.
You may refer to this article for details about making account deposits: How to Deposit Funds to Your Freelancer.com Account
Once your account reflects the deposit, you may then proceed with upgrading your membership. You can read this article to know more: How do I Upgrade my Membership?
Should you wish to change memberships, you can manage it at any time from your end by going to the Memberships page. Click on your profile picture at the top right part of your account, and select Memberships to be directed to the page:
An important thing to note is that memberships will automatically renew after the paid period (30 days) in order to save you the trouble of upgrading each time the paid period ends. So make sure to keep track of your membership start and end dates in order to manage it efficiently.