You can ask the question in the title if the answer is unknown. But if you're actually giving the answer at the end of the article, then what you did is nothing more than cheap sensationalism. -10 points for that.
This is absolutely contrary to journalism training. When you ask a question, answer it, otherwise it'll be a column not a news piece, no? (Unless you're presenting some kind of original research which would be nigh impossible in this case.)
Even if the answer isn't clear-cut (as in the case of "Should free digital TV channels be encrypted in SA?") the article should do its utmost to answer the question.
Also: often journalists don't write their own headlines, so don't assume the worst. That said, I'll own up and tell you now that on MyBB we usually *do* have to come up with our own headlines, so this was all me.
Someone asked this exact question of me on Twitter and I promised to find out from the operators if they had seen any change on BIS or performed any upgrades that might explain it. I got the answers, I wrote the article.
The headline is always the hardest thing to write, and it's even worse for an article like this where even people's observation that BIS had improved was refuted ("Vodacom/MTN/Operators improve(s) BIS speeds" would've been a great headline).
In the end I opted for this one because it represented the line of questioning that lead to the answer.