Ridiculous Waiting Period for Invoice

I thought the normal procedure is to be produced with an invoice for goods or services a customer pays for. I placed an advert in December 2015. The entire January past and not invoice. Nonetheless, maybe it is not Gumtree's policy to supply invoice unless requested. On 1 February, I requested an invoice for a paid advert that I placed in December. I did a follow up email on 3rd February and 7th February, until I finally got a reply on the 8th February. I was subsequently referred to Shalla in finance. I immediately sent Shalla an email on 8th February, I received a read receipt. By the 15th of February, I contacted Gumtree support again and was informed by Simone, she will get Shalla to contact me. I sent another email to Shalla on 16th February, I received a read receipt. To date no response from Shalla.<br> Please can I kindly have an invoice? Is is too much to ask or is there a one month or one year waiting period?<br>