For full context, see here: https://www.docdroid.net/XIK9pCk/img-20171020-0001-new.pdf#page=2
The sentence in question is taken from the very last two lines on page 2 of the PDF: ええ、ありますね。かならずしもうるさいチャイムやベルのおかげだとは思いませんけど。
I think that the person here basically wants to say
"because of the chime and announcement, I don't always do not think it is annoying."
My biggest problem though is that おかげで/おかげだ is used. I just learned in my textbook that this is used when CAUSE X has lead to POSITIVE RESULT Y. I get that the speaker, in case I understood this correctly, wants to conceal his/her negative opinion. But I feel very very unsure about this interpretation of mine ^^ Since I learned that おかげで/だ is used in positive contexts, I fear that it won't possible to use it inside a negative statement, unless irony is at play here. But I've no experience with irony in japanese so far...^^
Here's my full translation: (Very literal) "Yes. It sure is. But I do not always not think that (="that" due to と思います) because annoying chime and announcement."
(more paraphrasing) "Yes. It sure is. But I do not always not think so (= "I sometimes don't think of it in its function as a safety measure" see the pretext) due to the annoying chime and announcements."
I couldn't find a way to integrate the THAT in "I think that...". It never works because the clause it relates to is a causal clause at the same time. At least if I understood おかげで/だ correctly.