Worst service provider to deal with

Summer Mobile is nothing but ****msters I took out a contract with them on the 7 of February, received the phone 3 days later but it wasnt the device I asked for, they did collect it back from and never did a follow up, so they did deduct for March and April but still I don't have the device with me, I called in again 2 weeks back I was helped by a lady by the name of Melissa she promised to cancel my contract and refund my money which hasn't been done now no one is picking up my calls when I call in....

Can I get a call back or my money back and the contract canceled