Inmates at Waikeria Prison say they had to share one faulty phone between 80 prisoners for months and wait up to four hours at a time to call their family.
Once they got to the front of the line, the phone often cut out in the middle of the call, and it would cost extra for inmates to call their families again.
Fifty-eight prisoners signed a letter to the prison director earlier in the year complaining about the problem.
The phone was eventually fixed but the inmates are still unhappy about the efforts needed to phone home.
One inmate's partner told RNZ the situation put significant strain on their relationship.
"My partner had to wait in line for up to four hours at times for a 15 min phone call in which I could barely hear him due to phone static, it was horrible," they said.
"Corrections say they want to improve relationships between families but don't provide or care about the basic means to provide this being communication via telephone."
It was a similar story in Whanganui prison where, according to People Against Prisons Aotearoa spokesperson Jean Su'a, 60 inmates in one unit were sharing one working phone.
Her dad was one of those locked up. He had to wait in line to make contact with the outside world and Su'a said she was lucky if she managed to get a three minute phone conversation with him.
"I never have enough time to talk to him, I can't contact him when I need him."
Communicating with inmates in the unit is already a challenge as phone cards need to be purchased, Su'a said having only one phone added even more difficulty.
"The communication suffers so much, those bonds suffer, health and wellbeing suffers, it's just a domino effect which impacts every facet of a person's being."
Su'a said prison was already degrading and isolating and the extremely limited contact made it worse.
"It disrupts relationships, it can be really stressful for families not having enough contact with mothers, fathers, partners and children.
"It's an incredibly disruptive and unhealthy experience, and I imagine that everyone suffers through not being able to strengthen and maintain the bonds we have to the people that tie us to this world."
Doing the time was the punishment, it was not about having extremely limited access to contact with your family, she said.
Su'a said the problems at Whanganui Prison were ongoing.
The Department of Corrections disputed the number of phones available to the inmates at both Waikeria and Whanganui.
It said each unit at Whanganui Prison has between two and five phones, except for the intensive supervision unit, which has one phone but it has a maximum occupancy of nine, lower than other units.
Waikeria Prison director Jim Watson said Corrections knew how important family contact was for prisoners and it endeavoured to provide a range of options.
The lines went down during the riots in December last year and although they were fixed there had been issues with the pay phones in one of the units until November this year, he said.
"The affected unit accommodates a maximum of 80 men, and there have always been two pay phones in the unit.
"Both phones were successfully reconnected following the damage from the fires, but there have been ongoing issues with static on the line, and a small number of occasions where the phones have been temporarily down.
"This has always been fixed within a couple of days, with the exception of one occasion where one of the two phones was down between August and November this year."
Watson said staff requested a repair immediately, but the provider wasn't able to fix it for several months because of the alert level 4 lockdown.
"We acknowledge the outages and static issues affecting this one unit following significant fire damage were not ideal, but unfortunately sometimes technical issues are unavoidable.
"During this time, unit staff worked hard to ensure people were able to stay in touch with their friends and whānau."
Watson said since the repair was done last month, both phones in the unit had been operational, and the issues with static on the line had been resolved.
