Trouble recalling my dog outside at a park?

hi, first do short distances at home with one call... i would call my dog as DOLLY COME ( try to make voice higher when you yell come) i point to where i want her to be and treat as soon as she arrives. i typically get lower so i look more approachable. then move to back yard. than front yard while increasing the distance. always treat until they come EVERY time. move on to long leash at the park with treats, never repeat the word come. get their attention before you call.. it comes with time and practise. sometimes the brain comes with age. every pup goes through it. good luck!