Group C Car hire no automatic transmission

I am not happy with the car hire service, I have a group C car hire which does not say anything about an automatic or manual vehicle. I have requested for an auto car hire as I have not driven a manual in years and would struggle to operate a manual for 2 whole weeks while my vehicle is being repaired. I am simply requesting an auto transmission vehicle and not an upgrade of the car group. I do not understand why I can't get a Group A,B,C in auto as all cars come in either manual or auto transmission. The terms of the other group cars not coming in auto transmission is new and has never been explained to me. when I took my policy. All other insurers give you options on vehicle car hire transmission.