The fact that only H and J have groups of 4 sort of gives it away. Think of changing the letters to numbers (A=0) H and J would be 7 and 9 which are the only two numbers on a phone keypad to have 4 corresponding letters.

Convert letters to numbers (A=0) then convert from phone keypad cipher

2ath4phillipsz6n5o

Atbash the letters and numbers

3ofz7thenh8o7r

“Then” is not a valid keyword. The cipher used was Atbash so the reverse of Then would be Now

3ofz7nowh8o7r

16 pairs would make for a 6 letter keyword code. Make pairs:

75 56 56 38 25 38 96 56 28 76 27 76 35 07 75 87

Some values are too low to be valid Ascii letters or numbers. Look at where the numbers in the code should fall, notice how they all end with 5 (75, 25, 35, 75). We know that characters 2 to 9 in Ascii are 50 to 57 in decimal. Lets reverse each pairs

57 65 65 83 52 83 69 65 82 67 72 67 53 70 57 78

We now have a valid decimal to Ascii string

9AAS4SEARCHC5F9N