The list is for 2007 and is done by Brand Finance for top 25 global telecom leaders. I know this is old but found it appropriate to post.  This list is also appropriate in the wake of growing global ambitions of Indian telecom companies and growing Indian ambitions of global telecom companies.
Bharti Airtel has operations in Sri Lanka and Jersey. BSNL is bidding for license in African nation of Tunisia. Reliance Communications almost made a footprint in Africa with its proposed MTN merger. That deal did not go through. But, it did not stop the global ambitions of Indian telecom companies.
Even global telecom providers has increased their appetite for Indian telecom pie. Vodafone bought the share of Hutch to gain a significant foothold in India. It is the top brand in the world now. NTT DoCoMo has bought a stake in Tata TeleservicesTelenor bought a stake in Unitech WirelessMTS started its operations with its joint venture of Sistema Shyam Telecom and re-branded it to MTS India.
The study conducted by UK based brand valuation firm Brand Finance Plc, uses a methodology called “royalty relief”. This takes into account several factors mixed up to come up with the brand value of the company. Brand value is not tangible. (Trak.in)
Bharti Airtel with its brand is the only Indian company in the list. Remember this list is not based on the total subscribers. If that is the case at least 4 Indian companies and 2 Chinese companies would be on the list. This is based on the Brand Value or Brand recall of these brands across the world.

RankBrandParent CompanyBrand Value ($bn)
1VodafoneVodafone Group26.59
2AT&TAT&T24.6
3VerizonVerizon Comm24.38
4OrangeFrance Telecom18.35
5China MobileChina Mobile13.87
6Telecom ItaliaTelecom Italia9.43
7T-MobileDeutsche Telekom8.96
8MovistarTelefonica7.95
9NTT DoCoMoNTTC7.54
10BTBT Group7.29
11SprintSprint Nextel Corp.7.07
12TelefonicaTelefonica6.33
13Alcatel-LucentAlcatel-Lucent5.16
14America MovilAmerica Movil5.08
15TelstraTelstra Corp.4.64
16O2Telefonica4.62
17China UnicomChina Unicom3.45
18QwestQwest Comm Intl3.06
19SoftBankSoftbank Corp.3.02
20KDDIKDDI Corp.3.01
21TelenorTelenor2.97
22SwisscomSwisscom2.96
23MTSMobil TeleSystems2.79
24CNCChina Netcom Group2.55
25AirtelBharti Airtel Ltd2.48