Spectacles not received within 15 working days

Specsavers Tygervalley has been pathetic in giving the correct service. My husband went for an eye test on the 12th January 2020, He took the summer special for one set of glasses + one set free. There were said to him that he will receive his spectacles within 10 to 15 working days (monday - Friday). On the 1st February 2020, which was day 16 he received a second pair, after I had to phone them continuously the week before. To date he has not receive the first pair, and now I am told that he will only receive them by Friday, 07th February, which comes to 20 working days already. If you know you will have a backlog, please don't tell customers to wait 15 days, rather tell them 30 days, then we could have gone somewhere else, as oppose to wait this long.... I believe that this is bad service. Every time I phone the person answering say that they will follow up and phone me back, which they never do, I have to phone them again, and then there is just more and more excuses. We paid in full for the spectacles, and need them asap...