I think I would replace 'necessity' with 'request' to sound more natural.

"WE are used to CUSTOMIZING subscription opportunities AND ANSWERING to any kind of necessity." > One subject (we) and 2 verbs of the same tense ( customising and answering) We have experience in customising subscription business model, and we will be glad to answer any enquries,

We are used to customizing subscription opportunities + We are used to answering to any kind of necessity ===> We are used to "customizing subscription opportunities" and "answering to any kind of necessity".

We are used to customizing subscription opportunities and answering any kind of necessity.