Yes, Plivo API’s support concatenation. Though, some carriers and handsets do not support long SMS concatenation.
When sending a long SMS, Plivo’s Message API automatically breaks long SMS text messages into multiple SMS and adds a concatenation header to each message so that it can be stitched together (i.e., concatenated) at receiver’s mobile device.
Since Plivo supports sending SMS in all text based languages (e.g., English, French, Chinese, Arabic, etc.), text messages in any language will be automatically concatenated. Also all of Plivo’s Helper Libraries automatically encode messages into Unicode UTF-8 as needed.