How can I fix the Ask Always Option for selection of the sim cards to use

[cmukasauk]

I have a Galaxy S21 Ultra 5g but I can not find a Ask Always Option to select the different sims to use to make call. The sims are used to call two different networks hence I switch between the two sims, however the phone as makes the primary sim as the default for making calls and does not give me the option to use the other sim. How can I overcome this problem, otherwise it makes S21 Ultra 5g a wrong choice for dual sim users because they will always have to reset the sims to default sims to call the different networks.