Hi,
If you have only had you phone since July/August this year, then I suggest that you verify when you purchased it and as it is definitely still within the manufacturer's warranty period (2 years for the phone with provisos, 1 year for the battery also with provisos), consult the documentation that came with the phone as to what you have to do to make a claim for a warranty repair or replacement.
If you cannot find the documentation, here is a link to the Fairphone 2 warranty provisions
https://fairphone.zendesk.com/hc/en-us/articles/208652706-Warranty-Fairphone-2-English-