I am writing a letter to an organisation and wonder which is correct: "I have been to your store today and I see. . " or "I had been to your store today and I saw. . ." Which tense is correct and why?
Neither. See explanation.
In Perfect tenses (no matter if Past Perfect or Present Perfect) you do not put the exact time words like today, on Tuesday etc. They usually describe events without specifying time or using words like recently, lately.
In the given sentence Past Simple is the best choice: I was in your store today and I saw...