nestaway - Extra charges added illegally

I would like to highlight the wrongdoing by real estate management firm Nestaway. When we moved into our apartment it was managed by a company called Zenify. Our monthly rent was decided to be *****. This was including maintenance and water supply. I have rent receipts from previous months which shows that we paid ***** for a year and afterwards *****. This included all the charges except for electricity for which there is an electric meter installed for each flat.
Now out of sudden in the current month's rent, nestaway decided to add **** as tanker charges which they are forcing us to pay. The tenants have no information about how the charges are added. They weren't even informed or this clause wasn't even added in the rental agreement. When I had requested them to provide a new rental agreement we didn't get any definitive answers. As a tenant, we have every right to know how the charges being added. The water charges have to be added as per the usage like how it's done for electricity bills. Moreover, it was agreed upon that we don't have to pay anything extra for water supply as it is included. The pump is not working for the past many days and even though many people complained there was no action which was taken by them.
I would like to call upon the wisdom of the online community to decide :
*) If It is okay to add extra charges without the consent of the tenant.
*) If it is okay to modify the T&C and mutual agreement between the landlord and tenant.
*) If it is okay to charge the people any amount based on the supply and not on the consumption of water of each flat.
*) If it's okay for the customer to just ask us to leave or go for any internal transfer just because we have started questioning them on their misdeeds.