Dollar General

I was told I could only do one shopping trip per day. I can understand this with the same digital coupons but I was using my account twice in once day for seperate items, not different accounts. So we can only shop dollar general once per say now? What was the issue, with me forgetting an item the first time? I would like to know why their are different "rules" every time for a customer to shop by, and why I was turned away because I had already been to that store once that day?