This is the frustrating part to me. I bought a house with a broker I used a lot (flipped abused houses for a few years). He sold the loan to company A, which was great. They sold the loan to company B after a year, and the nightmare started.
One month, they withdrew my mortgage twice on the same day (found out when my debit card declined at the grocery store).
They sent a mortgage interest statement in January. I filled out my taxes, then after I had gotten my refund, they sent a corrected mortgage interest statement. I had to make a judgement call on whether this required re-filing taxes and the expense that entailed.
The worst was when we got a $2500 check from the mortgage company, saying they had recalculated our escrow, and they had overestimated it initially. We spent most of that money on setting up a nursery for a new baby. Two months later, we received another letter saying, "whoops, our bad, we actually did have escrow calculated correctly the first time. Pay us $2500 in 30 days or your house note is going up by $200 a month until escrow is funded again".
EDIT: Recalled another issue with this company. I'd get e-mails monthly: "You're late on your payment. We're about to foreclose on your house". This would be followed by an e-mail: "Our computer system is being upgraded. Please disregard late payment e-mails if you've paid your mortgage. We should have this fixed within three months".