Add note about Pro disk space increase via support

Author: beran-t

docs/billing.mdx

@@ -19,7 +19,7 @@ E2B uses [usage-based pricing](#usage-based-pricing) - you pay only for what you
 | **Disk space** | 10 GB | 20 GB | Custom |
 
 <Note>
-Pro plan includes 100 concurrent sandboxes. Higher concurrency up to 1,100 is available as a purchasable [add-on](https://e2b.dev/dashboard?tab=billing).
+Pro plan includes 100 concurrent sandboxes. Higher concurrency up to 1,100 is available as a purchasable [add-on](https://e2b.dev/dashboard?tab=billing). Higher disk space on Pro is available by contacting [support@e2b.dev](mailto:support@e2b.dev).
 </Note>
 
 Plans have different [API rate limits](/docs/sandbox/rate-limits).