Increasing Calls to REST API 1.1


Is there any possibility to increase the allowed amount of calls to your REST API 1.1?
Our service will post unique posts, defined and scheduled by the user, to their own accounts (statuses/update_with_media , statuses/update).

Posting and requesting statuses take place each 15 minutes and the service will check for the user’s posts statuses: retweets, favourites (statuses/show.json), amount of friends of retweet (statuses/retweets.json).

Minimum ‘post’ calls amount will be 30-40 (in future we would like to increase the amount ofusers) and minimum ‘get’ calls amount could be 120.
At this moment on our test account we have met the limits, so we would like to increase this rates. I have services such as Buffer that do not seem to have these limits so do you have some offers to increase allowed calls amount, and will it be possible to increase it in future, if we hit new limits?