Yes I'm struggling actually to find any time this place has been called Alto Volta. In French it was Haute-Volta, but it's never been Italian, Portuguese or Spanish as far as I know, which I suppose is where the Alto would come from..?
Also, "it's" should be "its". I drew the inference that English is your second language, and it's v. its is a little tricky and counterintuitive. The apostrophe in "it's" is not possessive, it's denoting the contraction for "it is". It's one of the exceptions.