[Company/ supplier address]
[Reference: contract number]
On [date] I [bought/placed an order for] a [item], received it on [date]. I have discovered that the [item] has the following problem: [add details]
The Consumer Rights Act makes it an implied term of the contract that goods be as described, of satisfactory quality and fit for purpose.
As you are in breach of contract I am entitled to have the [item] [repaired/replaced] and I would request that you confirm that you will do this within the next seven days.
I also require you to confirm whether you will arrange for the [item] to be collected or will reimburse me for the cost of returning it.
I look forward to receiving your satisfactory proposals for settlement of my claim within seven days of the date of this letter.
[Your name here]