Ordering on line & collecting from store

I ordered these shorts on-line for my son's birthday as the Kidderminster store did not have size 16 in store.
I collected them on Monday 12th May and upon wrapping them up for my son found that the tag attached to the shorts said size 16, but the label stitched to the waist was size 18. Obviously they are far too big.

After driving up to the store, they said they were unable to help,and I was told I had to contact customer services, which I then did. The lady I spoke to said I needed to send them back to them and they would then send the correct size out to me. I posted them at the Cost Cutter collection point on Saturday 17th May but have still not received the correct size of shorts. My son goes on a sailing holiday tomorrow, which is why I bought the shorts for him.
Also, calling your Customer Services is not a free line and it has so far cost me a lot of money as I had to hang on for ages whilst the matter was checked out.
I love the store, hence my recommended yes, but would say to anyone that if they order and collect, open the parcel and check that the inside label is the size you have ordered and not the tags attached to the shorts.