A320 First Officer reported they experienced cabin pressurization fluctuations and noticed both engines surging simultaneously during cruise. Flight crew elected to return to the departure airport and landed safely.

Narrative

We departed Runway XX headed to ZZZ1. During the climb I heard air rushing in the cockpit; in a pulsing fashion. We noticed the Cabin Press page was showing slightly abnormal numbers for that phase of flight. We agreed to get to cruise altitude and see if it stabilized; but it did not. The cabin altitude was at 7;250 feet at FL300 which was around 2;000 feet higher than normal. The cabin rate was fluctuating from +500 FPM to -500 FPM within a couple seconds and continuously. We could feel the bumping in our ears too; and noticed the outflow valve was constantly modulating open and closed trying to pressurize the aircraft appropriately; but could not. The left pack pressure was erratic and fluctuating between 8-40 psi within a couple seconds and constantly.Captain was discussing the issue with Maintenance Control and Dispatch via ACARS. Since there was no ECAM at any point; nor any guidance from Maintenance Control for a resolution; we as a crew elected to air return to ZZZ out of significant concern for safety.After we made the 180 degree turn; I noticed both engines were surging simultaneously with the pressurization fluctuations. I recommended we request priority handling; and the Captain agreed. The Captain briefed the Purser in accordance with SOP. ZZZ Center descended us slowly and we were cleared direct to the airport. During the descent we noticed the cabin rate was now +/- 1;000 FPM and could really be felt in the ears and sinuses. Because we had no guidance during this event; we elected to not change any pack or air configuration of the aircraft to not further any issues. We landed at ZZZ without further incident.