Is this complaining letter writing properly? Thanks in advance for helping me Dear Sir or Madam, I am writing to complain about the low quality of the internet sign on my mobile phone, and also about a huge mistake in the latest bill in which the cost of my new device has been charged twice. I have recently bought a Samsung phone in one of your central stores located in Gasteiz street. Although at the beginning everything looked right, just two days after buying the phone it became to run extremely slow; the internet connection constantly fails, and it makes impossible to do a phone call using the Whatsapp application as I am used to doing it. Besides, because of this bad connection, I can not review my social networks as frequent as I would like and this is extremely important to me as much as my job consists of being an influencer. As a dedicated customer, I hope you will work to resolve my problem and find a resolution. Otherwise, it would be my choice to change my current mobile phone account to another company. In addition, as I have mentioned before, there has been a big mistake in the last bill and I hope you to fix this issue and give me a refund as soon as possible (I am sending you a copy of such bill as an attached file). I hope to hear back from you about those issues. I can be reached by email at [email protected]. Yours sincerely, MR