Normally, systems that have small file size limits such as 2MB or 4MB require audio files to be in compressed formats such CCITT a-law, 8kHz, 8-bit wav mono. We can provide audio in any of these common telephony formats.
To give you an idea, in this compressed format files sizes are small. Here are some approximate examples:
1 min audio = 500kb
2 min audio = 1 mb
3 min audio = 1.5 mb
4 min audio = 1.9 mb
5 min audio = 2.4 mb