My take is that 挽钱 (wǎn qián ) would mean to withdraw money from an ATM and 换钱 (huàn qián) to change money ... or am I mistaken?a
No such saying as '挽钱'. It's not even a word.
'换钱' means exchanging money.
When you are going to withdraw money from an ATM, a Chinese usually says '取(qu3)钱'.
挽钱 might be a typo? 挽 can be used in the context of walking hand in hand (挽手), or deterring (挽留 - although this can be used in a positive context, like if you don't want your friend to leave). It can also mean resuscitation (挽救)