Pakistan's own Prime Minister says, "Beggars can't be choosers".
So, they have zero choices to make. They'll be forced to take a certain path. They'll be asked to back out of any Iran trade or agreements. Period. America calls the shots in their case. Straightforward.

My thought why Iran went to meet with them is possibly these 2 reasons:
1 - To try and manage the Balochistani problem where the Baloch freedom fighters are waging a battle to free themselves of Pakistani clutches whilst taking refuge possibly in Iran next door and same time also becoming a headache for Iran and
2 - Ensuring that Pakistan doesn't recognise Israel (under US pressure) at this juncture when Iran is putting its full force in handling Israel.
Threat of USD 18 billion material damages for non-fulfilment of the pipeline contract is the stick Iran will wield in case it doesn't get what it needs from Pakistan