Monthly 675 = Daily 22 approx. For 8 days of May, it would be approx 175. There is no advance monthly rental in BSNL. Security deposit is there and that would be 1 month of your rent, i.e. 675. Tax is around 12% I believe. Rs. 250 Installation charges are there if its a brand new connection . If you already had a landline, or there is some ongoing offer you may not be charged this or may have been charged a different amount.