Formal email/letter writing : correct usage of "issue which pertains to" / "issue pertaining to" /"issue that pertains to"

In my humble attempt at writing a classy formal letter, I am stuck with a bug in my brain .. probably due to my background of a non-native speaker of English.

I am trying to draw the reader’s attention to an issue related to my mobile device causing heating issues.

I wrote the following:

Dear Sir,

I would like to draw your attention to an issue pertaining to my recently purchased XYZ mobile overheating….

Should it be, instead:

I would like –"– an issue that pertains to my recently purchased –"–