Last Wednesday, customers from both islands took to social media to complain that they were not able to make calls, send texts or access the internet.
And Guernsey police issued advice, instructing customers to remove the sim card from their phone if they needed to call 999.
The outage was fixed a number of hours later with the company posting an image of the damaged cable on Queens Road online.
Although only mobile data and home broadband services were affected in Jersey, Guernsey residents were not able to make calls or send texts.
Rohit Khullar, head of network at Airtel-Vodafone, said: ‘We are very sorry to all of our Jersey customers who experienced an interruption of data services on the evening of 29 March.
‘Voice and SMS services were not affected. This was caused by a fibre cut from one of our suppliers and data services were restored that same evening.
‘We are currently further investigating the incident and will use the findings to improve our service resilience.’