Contact that don't end with telkom

I had contract with telkom for 2 years, the contract ended last December. They deducted the last installment December. November I went to tell them that I have no intentions to upgrade or continue . They told I must go online , you can ONLY cancel online. Contact 2 years goes until YOU cancel at TELKOM. WHY DO WE SIGN CONTRACT IF WE CAN STICK TO IT? prominade mall telkom told this story.