WhatsApp is battling mistrust globally after it updated its privacy policy to let it share some user data with parent Facebook and other group firms, and the backlash risks thwarting its ambitions in its biggest market, India.

Though WhatsApp has yet to see mass uninstalls of its app in India, users concerned about privacy are increasingly downloading rival apps such as Signal and Telegram, research firms say, propelling them higher on the download charts and putting those apps ahead of their ubiquitous rival in India for the first time.

The reaction in India — where 400 million users exchange more messages on WhatsApp than anywhere in the world — has forced the messaging app to unleash an advertising blitz costing tens of millions of rupees this week in at least 10 English and Hindi newspapers.

“Respect for your privacy is coded into our DNA,” WhatsApp said in one newspaper announcement.

It said its privacy policy update “does not affect the privacy of your messages with your friends and family in any way”. WhatsApp has also said that the changes to the privacy policy are only related to users’ interactions with businesses.

When asked for comment, WhatsApp referred Reuters to its published statements on privacy.

The media campaign — similar to one it ran two years ago when it was facing criticism in India for not doing enough to curb disinformation — underscores the severity of the crisis for the world’s most popular messaging platform.

Parent Facebook and WhatsApp have bet big on India and any user grumbling could dent their plans.

Last year, Facebook invested $5.7 billion in the digital unit of Indian oil-to-tech group Reliance — the social media giant’s biggest deal since its $22 billion buyouts of WhatsApp in 2014.

A huge part of the India investment hinges on a WhatsApp and Reliance project to allow about 30 million mom-and-pop store owners to transact digitally.

While WhatsApp’s payment service, approved by India’s flagship payments processor late last year after two years of waiting, does not fall under the privacy policy update, any sizeable user shift to other messengers could mean losing out to well-entrenched rivals.