The difference between 'due to' and 'because of'

They mean the same and can be used as alternatives of each other.
Also, 'a' won't be used before 'SMS'.
'An SMS. . .' are the right words.

One works as well as the other. Due to might sound slightly more formal, but there isn't enough difference to bother with.

Hi all,
thanks a lot.

The strict answer is that the word pairs “because of” and “due to” are not directly interchangeable. "Due to” is an adjectival prepositional phrase and “because of” is an adverbial prepositional phrase. In informal speech, we probably can get away with using them interchangeably, but they are not equivalent.

One trick you can use is to substitute “due to” with “caused by.” If the substitution does not work, then you probably shouldn’t use “due to” there. For example:

My low grade was due to lack of study.
My low grade was caused by lack of study.

The substitution works, so “due to” is being used correctly. Here is another example:

I missed the class due to the rain.
I missed the class caused by the rain.

The substitution doesn’t work here, so “due to” shouldn’t be used there. The correct sentence would be:

I missed the class because of the rain.