Very disappointed by customer service at Leroy Merlins Little Falls branch

Ordered fascia boards last year, on delivery 2 were short delivered even after I was assured they had all the stock on my invoice. I was assured they would deliver the 2 outstanding on the next delivery in a weeks time. After a few calls and visits to the store I was told that they accidentally sold the 2 owed to me but will phone me as soon as their stock arrives. I went in store last weekend to sort out the 2 outstanding and actually order more but was not prepared to pay delivery as they still owed me stock which were supposed to be delivered anyway (or even split the delivery cost 50/50). The manager on duty said he would sort it out for me and it would be delivered the same day. A week later and nothing had been delivered. I was phoned yesterday evening and told they had been trying to phone me (which is not true as I have answered all calls expecting them to phone for a delivery date). But was told that I must pay the full delivery price as instructed by management and now must come into store to pay for the delivery. I find this back and forth unacceptable and the overall service very disappointing. I work in the service industry and would definitely not treat customers like this. I have been calm the whole way through this process but I feel that this has definitely gone way too far.