unacceptable

I have a jet account and I always pay my account in an Edgars active store since its near my workplace.and suddenly my credit was increased without my knowledge.wen I requested d copy of a receipt where they claim I signed it was a horror,the lady forged my signature n worse she still denies she did it.i mean how can one be happy around their account wen things like dz happen???///?? Then yesterday got a call from someone demanding a payment from me since my acc is overdue wit R7000.00 whilst my credit limit is R1500.00.this is too much for me now.#disgusted