Disgusting service!

Good day

I am disgusted at the service from Ackerman’s .On the 23 December 2018 I went to Ackerman’s in Cresta mall as I had just had a baby and needed to change some of the clothes I received.The store did the credit and I choose new items.However I still had some credit left over so the lady handed me receipt for the balance .Today the 23 January 2019 I go to the Ackerman’s branch in Randridge mall to use this “voucher “ which looks like a slip stating the balance .I am told by the manager Linda and the salesman aswell that this is no valid and I need to give them the gift card .Firstly I don’t work for Ackerman’s and I tried to explain to them that this is the document I was given so I’m then told that I need to go back to that branch cos there’s nothing they can do .So now I must run around with my 6 week baby because of your incompetence.How am I as a customer to know your procedure that I should be given a card and not this slip .Further more this store could make no call or some arrangement to contact the other branch .Is this what u call customer service .Must I now take this “voucher “ of money that belongs to me and through it in the bin cos Ackerman’s messed up .