Sales error

Hello Sir\madam

This is miss Sinazo Dingani,i have a contract with cellc which i took last year in October 2019 hauwei Y7 2019 and i asked it to b Insuranced n the lady who was helping me told m it would b hollard paper i signed n left because I was on lunch n we did this phone contract for two days , so Saturday 8/8/20 i lost m phone in a taxi and i asked it to be blocked n it was n went to the police station on Tuesday n openned a case n got case number n then went to cellc Vincent n lady who rudely helped me said my phone is not under insurance who told m it was n i said the lady that helped m did n she said am looking at the computer nothing here so i asked so what must i do go to beacon bay n she said yes...so would love to know what should I do? Now am sitting with the bill over R700 without any explanation .

Thanks Miss S Dingani *** ***