If you look at the third definition of acronym, it directly addresses your question. BBC is an acronym, regardless of whether it is pronounced as letters or as a word. RAM (random access memory) is an acronym whether it is pronounced ram or are-aye-em.
There is a controversy as to whether initialisms are a subset of acronyms or a distinct class of terms.
Several dictionaries seem to restrict acronyms to those shortened forms that can be pronounced as a word. See, e.g., Oxford, Collins, and American Heritage.
Others include initialisms as a form of acronym. See, e.g., Merriam-Webster and Websters New World. Wikipedia has an article on acrnoyms which notes a difference of opinion as to whether initialisms should be included, and then proceeds within the article to include them. It also notes that there are a number of forms that do not neatly fit into either category, such as JPEG (pronounced jay-peg) and AAA (usually pronounced Triple A).
There is also the interesting evolution of an acronym found in the abbreviation for Standard Oil. It began with SO, a clear initialism, which them morphed to ESSO, a classic acronym. (The company has since become EXXON which does not seem to stand for anthing.