Details about Churches in Bangalore are available at St Mary's cathedral's website, http://www.bsmcathedral.org/Churches_Bangalore.html
This doesn't include the information about any Knanaya church, as per my understanding there are 2 Knanaya churches in Bangalore.
From christ university the Hosa Road church will be near by, around 6 KMS . You can take any bus going towards electronics City and get down at Hosa Road Junction ( Central Jail Junction) . This church is under construction and the services are conducted at the basement I guess. It is on the right hand side of the highway and one plot inside,there is one sign borad on the main road itself. You can see one Bakery along the highway and the chruch is behind that building ( Second plot after the bakery when you walk along the hosa road).
Holy Qurbano starts at 8.30 AM.
You can try Queen's Road Cathedral too, it is around 8 KMS from Christ College. There are 2 services on Sundays, 7.00 Am as well as at 9.00 Am. This is close to Shivaji nagar bus stand and Cantonment railway station. Contact details are given in the web site. You can call achan for any clarification on route etc.