put the whole plant, pot and all, in a bigger clay pot for the time being.
When you repot, cut off any of the stem that is rootless, and use an approrpiate pot size.
Many, but not all phals do try to grow sideways. Doritis hybrids are mostly upright, but those with violacea in them try very hard to grow sideways. This is healthy for vios, because they are susceptible to crown rot, and the slanting crown helps keep water out.
However, I do straighten mine from time to time. I use a styrofoam peanut (or fragment of peanut) tucked under the crown to straighten it *a little*. Use a very soft hand, and raise it a very little at a time, maybe 1/4". You don't want to break the crown.
You can also give up and let them grow the way they want to
. Nature always wins, anyway.