As in how the name of the letter is pronounced? I don’t recall hearing people here say ju instead of ji for the English pronunciation of the letter G.
Using the letter “G” to represent “jī” (雞/chicken) is a common substitution here – and a good match phonetically. For example, one can find menus or store signs with “G排” and “G丁” rather than “雞排” and “雞丁,” respectively.