A professional dog trainer should help you distinguish a rusty skill from a different problem. If an adult dog used to come when called but now struggles around unfamiliar dogs, describe the whole situation. Reactivity, fear or difficulties during socialization may call for a different assessment from an ordinary recall review. Separation anxiety also needs its own discussion rather than a general obedience refresher.
Ask how the trainer will help you teach your dog again without relying on endless repetition of an unsuccessful cue. When you ask your dog to sit, for example, the instructor may want to observe the signal, your position and when you reward your dog. This gives both of you a concrete exercise to review and shows how the dog learns from the current interaction.
Explain any changes in pet care, such as a new walker or another family member taking over lessons. Ask the dog trainer how everyone can use positive reinforcement consistently and share the same training goals. Dogs need instructions that make sense within the routines they actually encounter, so the refreshed plan should include the people responsible for those routines.