Tata Sky - They didn't send me the invoice

Tata sky didn't send me the invoice of the set-top boxes & channel package which I bought on **/*/**. First, they told they will send the invoice within * hour, then they wanted sometimes. Whenever I call, they told today you'll surely get the invoice but they aren't sending. Mr Ali told on **/**/** that he'll send the invoice but he didn't. Then I chat with Mr Althusser Pandit, he told me within* hour, he'll send but he didn't. Mr Aman told he'll send within * hour but he didn't. Mr Arun told I'll get the invoice at the end of the month. Then Mr Tanmay told I'll get the invoice in my mail but I didn't. Mr Manish told I'll get the invoice after the month. Today, * lady called me that Tata sky doesn't have the facility of sending the invoice. Today lady from Tata sky called me that I will not get the invoice.
Each & every person is saying different. Intentionally, they want to give trouble to the customer. They are so much confused. They don't know even their rules & policies. Seems that uneducated people are working in Tata Sky. It's their duty to send the invoice. Again today, I got the call from Mr Rajkumar, he said he'll send invoice still I didn't get.