If you consider the scenario of dictating over the phone, letters can be confusing not just because of their written shape. For many non-English speakers, for example, E can be confused with I, and V can be confused with W, unless both sides use the same way of pronouncing them. Look how Microsoft's base24 alphabet (from the other comment) has neither E nor I.
In this case the phonetic alphabet will do the job only for English-speaking countries (or at least those that are very well accustomed to Latin characters).
