No refund from coop

Reptile11

Hi new here just getting advice.I recently moved house informing coop energy 1 month in advance . Read meters 28th July contacted same day with readings and confirmed move, new address phone and new email.I have since phoned them 3 occasions to chase up final bill.We were in credit by approx £500. Each time they informed me that final bill being generated and will take 3 to 6 weeks, They fail to provide any confirmation of calls or account requests in writting/email.
Last phone call to them today same result and they claimed not to have new phone number and email address.
I still have access to my old ISP and emails no contact has been made by coop energy.
What should my next step be
Thanks
reptile

Nada666

It's a pity this is your first post as I had an excellent reply playing on 'flying the coop' but it would have been unhelpful in content so as a response to a newbie I can't use it.