There are many Test Centres for GMAT Exam in Mumbai. I am providing list of all Test Centres:

Pearson Professional Centers-Mumbai
Building No.9, 1st Floor
Solitaire Corporate Park,167 Andheri
J B Nagar Link Rd,Chakala,Andheri(East)
Mumbai
Maharashtra 400093
India

As you want Test Dates for GMAT Exam, so you should contact to the Test Centre. Go at this address and get details about important dates.

Here I am providing contact details of other Test Centres in India:

GATS
Office 1
Symphony 'C', Ashok Nagar,
Range Hills Rd,Off PuneUniversity Rd
Pune
Maharashtra 411020
India

A1 Professional Assessment Center
A/709, Titanium City Centre
B/h IOC Petrol pump, 100 feet road
Near Shyamal Cross roads, Sattelite
Ahmedabad
Gujarat 380015
India

Sarva Mangla Maa Samiti - Inspire Me
611, Shekhar Central,
Palasia Square
Indore
Madhya Pradesh 452018
India

Edu- Kinect
Plot no 179, 5th floor,TSS towers
B-wing , Kavuri Hills
Madhapur
Hyderabad
500081
India

Pearson Professional Centers-Hyderabad
1-10-72/A/.2, Pochampalli House,
3rd floor, (Above Nike Show room)
S P Road, Begumpet,
Hyderabad, Telangana
Andhra Pradesh 500016
India

Dr. T. M. A. Pai Polytechnic, Manipal Campus
M. I. T. Campus, Eshwar Nagar
Udupi
Manipal
Karnataka 576104
India

Lakshmi Narain College of Technology Excellence
Kalchuri Nagar,
Raisen Road,
Bhopal
Madhya Pradesh 462021
India

Unisoft Technologies
2nd Floor, Parnanda Building,
Above Now & Wow, Besides Khadims
West High Court Road, Dharampeth
Nagpur
Maharashtra 440010
India

MYRA School of Business
Near Infosys,
Opp. Power Grid,
Yelwal
Mysore
Karnataka 571130
India

Pearson Professional Centers-Bangalore
# 45, 3rd Floor,Trade Center
Dickenson Road
Next to Manipal Centre
Bangalore
Karnataka 560042
India

KL University
Green Fields, Vaddeswaram
Guntur
Vijaywada
Andhra Pradesh 522502
India

Tec Education Foundation
A 152 Block 12
Gulistan-E-Johar
Karachi 75290
Sindh
Pakistan

Sakar Edutech Pvt. Ltd.
Office No- 404, "Shyam Anukampa"
O-11, Ashok Marg, C-Scheme
Opp.HDFC Bank
Jaipur
Rajasthan 302001
India

Vellore Institute of Technology
Centre for Technical Support
Thiruvalam Road,
Katpadi
Vellore
Tamil Nadu 632014
India