If you feel the punctuation is 'off', you are probably writing the way you speak. We often ask questions at the beginning of what ends up being more of a declarative sentence, because, if it were written out, it would actually be:
Was there something changed recently? Because internet shouldn't be dropping this low, even for a small plan.
That's why it takes more thought to write than to speak.
If you want to write very informally to friends in a text or similar venue, no one will arrest you for doing just as you have suggested here. However, if you're going to write where it's a bit more important how you present yourself, you'll just have to be aware that your punctuation is not usually used.
You can either write it as two separate sentences, or rephrase the sentence so that your question comes at the end.
The internet shouldn't be dropping this low, even for a small plan; has something changed recently?
When you write your own book (or blog/whatnot), if you don't care what people think of your writing, you can punctuate (or not) however you like. Jonathan Coe's The Rotters Club, published in 2001, contains a sentence with 13,955 words. I don't know how it's punctuated.