Pink / Purple dots on iphone 5s camera

Have you visited an Authorized Apple Service Provider or Apple Store? Usually Apple does not offer to change just parts of the phone, besides screen replacement for the iPhone 5 and 6. If your phone is not covered by warranty anymore, they will offer you a replacement if you are willing to pay the Out-Of-Warranty-Service fee:

Out-of-warranty repair service
If your repair isn’t covered by Apple’s One Year Limited Warranty, AppleCare+, or AppleCare Protection Plan, your iPhone might be eligible for out-of-warranty service. For example, liquid damage isn’t covered by warranty but might be eligible for out-of-warranty service. Some damage isn’t eligible at all, for example if your device has been broken into multiple pieces. See Apple’s Repair Terms and Conditions for complete details.
Read Apple’s Repair Terms and Conditions

Model	Out-of-warranty service fee	Battery service*
iPhone 6 Plus	$329	$79 *available only if battery fails Apple’s diagnostic test
iPhone 6	$299
iPhone 5s, iPhone 5c, iPhone 5	$269
iPhone 4s	$199
iPhone 4, iPhone 3GS, iPhone 3G, Original iPhone	$149

Plus a $6.95 shipping fee, if required. Fees are in USD and exclude local tax. Pricing is for service through Apple. The final service fee we charge will be determined during testing and may be less than the service fee listed above. Pricing and terms vary for service through an Apple Authorized Service Provider.

copied from Service Answer Center - iPhone

Yes, you're correct, the service for your country might be different, the above has been copied from the service options for the USA.

In your case it just says:

Out-of-Warranty Service

Please contact an iPhone Authorized Service Provider for out-of-warranty service options.

copied from Service Answer Center - iPhone /India

So, if the Authorized Service Provider says they will replace the camera only, there is nothing you can do about it. The repair will covered by a short warranty period as well.