Shocking after-sales service from Leroy Merlin

On 28/09/21 I ordered a pond pump impeller and pond pump filter case which were advertised to fit a Waterhouse WH1200 submersible water feature pump. The items were delivered on 30/09/21. Without needing to open the packaging, it was clearly evident the items would not fit the WH1200 pump. I immediately emailed *** requesting the correct items be sent or a refund. I included photos which clearly showed the items sent were too small for the pump they were claimed to fit. On 3/10/21 I received a response from a LM representative who said he had alerted the supply chain team and they would assist. On 13/10/2 I rep**** to their email to follow up and asked for the case to be escalated. Subsequent to my mail I received a phone call to say one item would be replaced with the correct item, and the other item would be refunded. Several weeks later the items were eventually collected. After hearing nothing further I received an email on 31/10/21 with details of a refund which is for the items ordered, but not the delivery fee, noting that the funds would take a further 7 to 10 working days to appear in my account. On the refund detail document it says "CHANGE OF MIND", which I assume means that they have recorded the reason for the refund as the customer changed his mind. I did not change my mind at all! The order process was smooth and the goods arrived promptly, but what's the point if the items are advertised incorrectly and then it takes more than 2 months to resolve? And I don't get the delivery fee back! I will definitely never order anything online from Leroy Merlin and they will be the last place I will shop.