Incorrect invoice

Dear Sir/Madam i hereby would like to express my query on this Platform. i took a contract with cell c in October i always make payment on time since i took the contract i never skipped payment. i was surprised when i received my statement on Friday the 12 of February the invoice include a hundred rand they say i reconnection fee my services where never disconnected i would like to disputed the invoice i have received. Somebody please sort this out