Tell me...... is this good business practice?

On Sunday, a party of us are dining out as we usually do in January, exchanging presents because we normally do not see each other between the beginning of December, and the beginning of January each year.  This party involves one elderly lady who loves to come out with us and meet all her younger friends.

Two days ago, I booked a table for 7 at a gastro-pub.  This morning I hooked up with 2 other friends who we had thought might not be able to come and they said "yes please!".  Now, all I have to do is phone the pub and ask if I can bring 2 extra diners.  The immediate answer I got was, "No, you can't".

I asked if I could fit two more chairs round the original table but was told no, as it was a tight squeeze already.  Mmmmm.  "I don't want to cancel the booking, I would like you, The XXX Arms, to have my business....... can you help?"  "No, Sunday is our busiest day, and we are already nearly fully booked".

Now at this stage, you might think that I would just cancel and go.  But the elderly friend was really looking forward to eating at this particular venue, it having been closed for a while, re-opening only last Summer, so you will understand that I pressed on..........
ME "Do you perhaps have a table for 2 available?"
THEM  "Yes, but you do understand that you will not be near the original table?"
ME  "Yes, but I presume it will be in the same room so we will be able to wave at each other!"
THEM "Yeeees...." 
ME "I'll take it" etc.

Now I have a dilemma.  I really want to talk to the management about this.  I should not have to tell staff how to handle a customer and keep their business (perhaps an offer of two tables, one for 4 and one for 5 would have been the way to go).  I also know that as we get older, our basket of common sense is brimming over with good ideas.  But if I tell the management how this was handled, it is the girl who answered the phone who will be in the soup, when in fact I see a gap in staff training here which is clearly management's fault.  What would you do?

EDITED TO SAY ..... yes I did phone them.  I asked for the Dining Room manager, and explained my dilemma.  He understood, he would sort this out before we got there, and he took my point about staff training.  We arrived on Sunday, and everything was as it should be, two tables next to each other - one for 5 or 6 and one for four, which they then offered to join up.  We took that offer and had a lovely lunch with very attentive staff, and enjoyed our annual meet up.  I have learned that it was the right thing to do, to bring this problem to their attention, and they have learnt that a happy customer is a tipping customer!  Win-win!