Hi Suganya,
As Clint said, there are no prebuilt extensions, but it's easy to write a javascript code extension that will do the job. Sometimes individual tag vendors provide some code for doing this, but if your vendor doesn't, we can help.
Perhaps you'd like to share with us which letters you'd like to convert and I can write some sample code for you?
Craig.
Check out our new Swift integration library for iOS, macOS, tvOS and watchOS: https://github.com/Tealium/tealium-swift with updated
documentation https://community.tealiumiq.com/t5/Swift/tkb-p/swift.