NOT ENOUGH POSTAGE WAS PAID (WHEN IT WAS) This week some of my customers have been receiving a grey card saying "Item underpaid - there's a fee to pay". These items are all LARGE LETTER 35x24x2cm 300 gr - they all pass through the Size Guide - RM is asking my customers to pay £3.50 (as if they were small parcels) to collect the items (when I've already paid £2.39 for each one of them). I'm 100% sure I've paid the correct amount - I send out 30+ items per day, 4500+ in 11 months - never had this kind of problems. I've been calling Business Customer Service since Tuesday and no one has been able to solve this yet nor to give me any explanations. My customers are obviously disappointed and I am embarrassed and disappointed as well. They are and might be leaving bad reviews and for an e commerce reviews are everything. Other than this I've been waisting so much time this week replying to all my customers, sending complains, making calls and yet no answer. I'd expect a decent service considering that I am paying Royal Mail £2k + each month in postage labels. This is so un professional and annoying. PS. To stay on the safe side I've decided to ship all my large letter from my local post office instead of buying labels online - at least till someone will give me some answers. At my local post office all these items are labelled as LARGE LETTERS and I am paying for LARGE LETTERS.