Bad as for the subject of invoice, I had been prom...

Bad as for the subject of invoice, I had been promised from minute 1 that I was left in an amount including VAT that seemed good to me, being a company, a new customer and for 2 simple products, they offer it to me for 12 months, so far perfect and contract with them, but ... I've been since February with all the invoices charging between 15 and 20 more every month, I have to claim every month, they give me the reason and they are returning every month as I claim, but they tell me that they leave it solved, in summary I get it back, but it is still an incorrect amount and here I continue trying every month to solve it ... As for the fiber, I have no complaint since it is perfect, but it takes me away eager to include more services, due to the problem of error regarding the collection of the invoice.