Lost Phone and IMEI No

On The 23/12/2015 i lost my Samsung S4 Mini. 0n the 24/12/2015 i went to Vodashop and report the lost phone.They ask for the make and IMEI no. They could not get the IMEI no on the system and phone vodacom customer care to block the phone before the claim can proceed. Customer care claim that i only had my sim card in the Samsung S4 Mini on the 18/03/2015. I told them to give me the IMEI no of the phone i had my sim card in for the rest of the year till the phone got lost. They can't give it to me.How did i used the contract then. Do they think i paid my contract and never used it. Please help me with this problem. IMEI ***, cell ***.