Extra contract taken without my knowledge

I took a ****le for R269 per month and I've had it for like 4 months. Recently a debit order of R899 + R269 went of. Went to the Telkom store IN mall of Tembisa and they had advised I took the contract. I requested the proof of signature whether by voice or actual signature and they had advised its not available and said I took it online. Which I don't remember. May we please resolve this as it's too much money and I'm suspecting ***** on my account.