Yashtel plans, charges and billing - hide and seek

Recently renewed my internet subscription with Yashtel. But the charges, duration and billing raises some questions. On the plans page they show plan charges + Tax.. They don't say what tax and how much! I am assuming it's 18% GST. But, after purchase, they didn't send me any invoice or receipt. Their support confirmed that my plan is renewed. When I asked for a payment receipt, they say they will give only to GST registered business, not to individual customers! Sounds a bit shady. BSNL used to promptly provide a receipt with plan charges and GST break up. Did any Yashtel customers here get any receipt?