A319 First Officer reported receiving a Yellow Hydraulic Reservoir low ECAM message during cruise requiring a diversion.

Narrative

Hydraulic quantities were checked on all systems during the preflight and all systems were in the green band. The preflight walk around did not have any indication of a past or current hydraulic leak. Departure from ZZZ was normal. Upon reaching cruise altitude; we ran through the screens to check all systems. We both noticed that the yellow hydraulic system had an unusually low quantity indication - about ' - ¾ of the way to the yellow band. About 10 minutes later; we received a Y HYD RSV LO ECAM. We completed the ECAM and FM (flight manual) procedures. The CA then attempted to contact data exchange and Maintenance Control via ARINC through a call me" ACARS. The initial frequency we were given was very broken and unreadable for the most part. We were switched to another frequency and that seemed to work better; but then seemed to completely stop working after about 5 minutes. We sent data exchange an ACARS that we were planning to divert to ZZZ1 as it was the nearest suitable airport and we were having trouble with voice communication with them. I estimate we flew for at least 60 miles; probably more; while we were trying to sort out a suitable voice link to dispatch. We [requested priory handling] with center and asked for a diversion to ZZZ1. Landing numbers were uplinked and we validated them with the FM tables. Landing on ZZZ1 was uneventful with the ARFF (Airport rescue and firefighting) standing by for the possibility of hot brakes after landing. No further assistance was needed and we taxied to the gate and deplaned the passengers via the jetway as normal."