Can I have 2 currencies in my Steam wallet?

[Xavier]

Say I have some pounds in my steam wallet, and I want to top up, but the only currency available is dollars. What will happen? Will I have 2 currencies or will it all become pounds?

[Marshal]

Based on your location, steam should automatically convert the amount in your account to your current location. Say you are in US, your currency should automatically convert into dollars from pounds in this case. It should convert the older currency but try contacting them and ask for help.